****ty company who don’t prioritise their customers

I am not sure what i need to do to get this company to respond to emails or pick up incoming calls. I have sent numerous emails and called multiple times just to change my debit orders details because i have changed bank.. next thing they will put me in arrears or block my network because they didnt get their funds.. i so regret why i took fibre with them in the first place.. i ignored the reviews now im in a mess