Resolve issue with Meta - Lost Business Manager account access

Hi,
Please send your proposal only if you have prior experience successfully resolving similar issues.

We're a looking for Meta expert. A previous employee or agency created our business account and did not provide us with the login credentials. As a result, we are unable to determine the owner of the existing business account and cannot access it. Therefore, we have created a new business account and need to disconnect the old one from our Facebook page and connect it to the new account.