Stuck on Background Check: What to Do When You Can't Provide Manager Phone Numbers?

I have recently accepted an offer. As most companies do, they will conduct a background check for which they have hired a third-party vendor. However, the third-party vendor is insisting that I provide phone numbers for the reporting managers of all my previous organizations.

There are a few problems:

1. My current manager has not shared the phone number; I only have the manager's official email address.
2. I am not in contact with all my previous managers, so I do not have their contact details.
3. One of my previous organizations has been sold off, so again, I lack contact details.

Does this mean my background will never be verified, and am I always at risk of not receiving an offer from a reputable organization? This is because I am being told that I HAVE to provide the phone numbers.

If they insist so much, why don't you give it? After all, it is a verification of your past service from your previous employers and not like any police verification. Nowadays, the organizations hired for doing such background checks act like detectives, and the way they approach is like an investigating officer trying to find some fault. Let them do their work. If you are confident in your abilities and employability, why should you worry?

Dear Madhu, It is not that I don't want to provide the phone numbers, nor do I doubt my capabilities. The question was raised for practical reasons; I may or may not have the phone number of my manager from 15 years ago. Fifteen years is a long period. I am not in contact with all my managers, and therefore, I don't have their phone numbers. I do have their official email addresses. However, the verification company insists only on having phone numbers.