Sounds to me like you are being deliberately set-up to fail, but yet you need the job, and don't want to throw away 23 years and have been productive in other roles, less productive in this one.

They on the other hand may figure they can get someone in to answer phones, data input, etc. cheaper.

Don't answer this, but how old are you? How old are the others that are not putting in their fair share of the time on the phones?

Keep answer to self. Just ask yourself this.

Do what poster said above re: ADA and presenting a solution to your managers. Keep possible age issue to SELF, do not bring up with employer.

Take up chain, step-by-step, documented (and kept at home) every step/conversation, etc. you have re: above.

Be pleasant, polite, work with your boss on alleviating some of your issues regarding not being able to devote your attention to your clerical tasks while answering phone, no uninterrupted time, explain to boss you need a few blocks of time uninterrupted to ensure the quality of your work, see if you can't wrangle this out of them.

The quality of your work is/will suffer. You performed well in prior position and want to continue to perform well; however, with being given no break off phones, the quality of your work, efficiency and productivity is suffering.

It's not about you, it's about what you do for the business that counts; do what you do best that helps the company succeed.

I wouldn't jump to conclusions, just keep above in mind. Proceed cautiously, continue to do the best job you can in the process, see if you can't transfer out of position into something else if they can't keep you in your "old" job, prior position.

They are basically changing your position (in a very covert, passive/aggressive way, which is sneaky) without presenting you with new job definitions, so it's up to you to clarify all of this, i.e. is answering the phones all day my new job? Do so professionally, factually, and in a non-defensive manner focusing on what you do best for the company.

You need to draft your questions, type them up, ask for a 15 minute meeting with manager to briefly discuss, and send questions via email in "preparation" of the 15 minute meeting you ask to set up, then keep all documentation (copies) at home if your managers are being less than honest.

Look, company doesn't have to keep you, but at the minimum they can stop the happy horsehit jacking you around and be honest about what their intentions are, the email/questions and feedback will flush any skunks out so you know WHERE YOU STAND and can do what's best for you.

They could be preparing (and/or already in progress)of rolling you big time, or, they could just be lazy and don't like conflict and don't want to "force" the other employees (they made too much of a stink) whereas you just went along with the program so you are the "easy" solution.

Force your manager's to earn their pay in this situation and actually manage instead of passing the buck to the easiest employee to pass it too without conflict or resolution.