Can't log-in back to FB Messenger account created with phone number

1. Initial FB messenger account was created with phone number (without FB account)

2. Changed smartphone

3. When logging in with the same phone number, a new clean account was created. Contacts & groups are not synced. Original account is still present in friends’ chats.

4. When I try to re-log-in with same phone number, I get into this duplicate account. Can't access old original account.

Resetting password didn't help. Logging-in through web on messenger.com takes to this new duplicate account. Searching for account here also finds only just new account. No reply from FB support after reporting the problem.

I see people report same problem here, here, here.

Thanks so much for any hints to solve this problem!