Bad service

Due to a mistake on there side in July 21 my acc went in arrears. Everytime yhey phone me for upgrade they say my credit score is high and will contact the creditors department and will come back to me. They never come back to me. I have 3 contracts with them for s long period. I think their service is really bad. The account was never behind and I paid the autstanding amounts as they saod if the account is up to date for 3 months I can do an upgrade that never materialised.