The blackmail was to ensure that they would not reveal the company, which after all was killing people
Excellent point.

what would happen the third time he called, me i'd ask if there where any loyalty card discount's, 2 for 1,Friend referral discount, that kinda of thing.

Altho73, I guess the screenwriters had this matter in mind, and consequently they wrote the "writing under prize cup" sequence at the beginning, so that Arthur really is brought to believe it can only be his "dead best friend" who calls him. At the beginning, he has the spontaneous reaction that you'd have :he thinks the guy on the phone is a psycho.
Then again, as a spectator, you have to believe that he believes, otherwise if you really want to object to "unbelievable" points in this film, there could be many others

'but i think once you get the phone call, it means you have no choice'

I would disagree with that. If a supposedly dead friend of mine rang me and told me that he was still alive living under a new identity with a rejuvinated and surgically altered body from a service provided by a secret company, I would shout down the phone, 'P*** Off you sick jerk' and slam the phone down.
If he called a second time I would shout at him that the police were now being informed and slam the phone down. That would be the end of the matter, there would be no third phone call.
My guess is that many prospective new clients would turn down the offer quite simply because they would refuse to believe it!!!!!

You explained it so good. For me at least.
"Those who cast the votes decide nothing. Those who count the votes decide everything."
Stalin

The company already has their money and now it has an extra body for Cadaver procurement. Why would it care if it has a high failure rate? they dont care of the rebirthing procedure is 'perfect'. In fact its better for them if its not.
I have to disagree with that. If the company runs the way you describe, then why does it hire employees like Nora Marcus to help reborns adjust to their new lives? Why not just blackmail potential customers under the
guise
of giving them new lives, then kill them and take all their money? Why invest the capital in employing top-notch surgeons, physiotherapists, psychologists, and researchers if the sole goal is expedient profit?
The reason is that, like any company, this one came into being because its founder(s) believed it could deliver a service that people were willing to pay money for; and, through that service, it would eventually become profitable. Like an astronaut exploring the new frontiers of the universe, the old man (Will Geer's character) envisioned himself developing something advanced, futuristic, and profound. As with many other corporations, this goal or service was not completely noble: only the very rich would benefit, corpses had to desecrated, etc., (and if it murdered people to provide corpses, then the company was not noble at all, but instead truly evil). But the point is that it had already invested in its promised service, just as a utility company or a telecommunications company invests in power grids or fibre optic networks. Its success does not lie in sabotaging its own service.
A high rate of dissatisfaction would be the death knell of the company because the disillusioned reborns would be more likely to return to their previous families, confess what happened, and expose the company to outside authorities. This is why the company hires people like John to act as "butlers" (i.e., spies) to new reborns. If they show signs of regret, then they become dangerous and are taken out. The company's success lies in reborns' satisfaction, since this would lead to more enthusiastic referrals, more clients, and more profit.
Also, I don't believe the company
relied
on dissatisfied reborns to supply them with cadavers. When the company started out with its very first client, it would have had no "cadavers-in-waiting." The CPS (Cadaver Procurement Service) would have either scoured recent death reports for the right physical match, or (more sinisterly) killed unsuspecting outsiders who were the right physical match. Using failed reborns as "cadaver stock" became a way to recoup the monies spent on reborns who couldn't make a go of it. It was a
cost-saving
measure, not a
profit-making
one. Far from becoming the company's
raison-d'tre
, it became, IMO, a desperate method to keep the company solvent in the face of an unexpectedly high failure rate.

It seems that the corporation forced (by blackmail) Arthur to become one of their reborns. Why were they so bent on recruiting him? I know they obtained his name from Charlie; so does that mean that each existing reborn was expected to provide a subject (or a "guinea pig," if you will) to the corporation so it could continue to perfect its "rebirthing" procedure?
Money and secrecy.

1. The blackmail was to ensure that they would not reveal the company, which after all was killing people to provide cadavers for new reborns.
2. Its all abut money. The reborn provides an allowance for their family the rest goes to the company, from which the reborn takes an allowance.
   If the reborn fails, they are stored in 'dayroom stock' until a new reborn matches them and they are taken by Cadaver procurement for the simulation of that new reborn's death.
   The company already has their money and now it has an extra body for Cadaver procurement. Why would it care if it has a high failure rate? they dont care of the rebirthing procedure is 'perfect'. In fact its better for them if its not.
   Existing Seconds were expected to provide new customers to bring in more money. Perfection was NOT a consideration.

If Arthur had been given a chance to think it over, do you think he would have taken the corporation's offer and signed up for a second chance at life?
I would tend to think not, they relied on rushing people and playing on their disllusionment and despair. I would have hoped Hamilton might have, given time, come to count his blessings and remain Arthur.
The point of the movie remains though:
Rebirthing didn't work
No matter what changed externally he was still Arthur Hamilton

i don't think they had it out for him specifically, but i think once you get the phone call, it means you have no choice. the corporation does thrive off of those who are recruited by other rebornsand when SPOILER tony is taken to where charlie is, we understand that they have two choices if they want to be reborn again. they can either give a name (the way charlie gave arthurs)or they get terminated.
i think if arthur had been given the chance to think about it, he wouldn't have. it's toounconventional. one of those things where if you were't "forced" to do it, he would be afraid. Yes, he had a very drab life and wanted to change, but i don't think the thought ever entered his mind until the proposition presented itself. he was talked into the idea because he had to be.