Verify Deposit Method - Natwest

We have failed the Verify Deposit Method process - Amazon have requested a "stamped and signed" statement or letter from our bank confirming ownership.

The original statement we submitted met all the requirements, we believe.

The bank account is in the name of our LTD company which is the same as the Seller Account, at the same address.

We have enquired with Natwest about getting a stamped and sighed letter or statement, but they will not provide either.

Has anyone got any advice on how to proceed with this.