how do you get in tiuch wigh thd complaints department when they do not bother to answer your complaint?

I raised a complaint through a chat and then had a call from someone who said they’d get the complaints department to call me - this was on the 26/9/20 and I’ve not heard anything as of the 17/10/20 Three Weeks later. I can’t use the app as that’s the complaint. I used to be an id customer, left a year ago the come back but now can’t use my email address for the app. They say I have to create a different one which I’m not happy with. Why should I have to? Surely this is not a difficult thing to resolve? I am however really frustrated at how difficult it is to contact you. PlEASE WILL SOMEONE RESPOND