NO REPLY ON CHANGING MY BANK ACCOUNT WITH THEM

We have send multiple emails through to RCS to change my fiances banking details because he switched banks they are not responding to me or my BANK my bank called me just know to say it's been 3 weeks and no word from them to confirming that they approve to take the debit order from the new account there is just no service, when you call the call center there is always a HEAVY FLOW OF CALLS!!!