[GB] formal complaint?

I need support..

Registered a formal complaint over 15 days ago now, Revolut have yet to respond and I need a final response letter or email for the FOS....

Pretty major complaint regarding an incorrectly placed CIFAS Marker to which they have since removed, but the complaint regarding them placing the marker incorrectly and the affects it's had has went unanswered.

anyone had any similar situation or any better ideas on how to get a response?

cheers!