Welcome to this forum.
This is a customer to customer forum only, where forum members, who are only BT customers, can help each other with BT Retail products and services.
Anything you post here does not go to BT. Although the forum is moderated by BT, not all posts are read.
If you would like to try Live Chat they should be able to help you.
The only other option is monthly payment plan, where you can alter the payment date.