WORST SIGNAL EVER

I have a contract with Cell C for 2 x Huawei P20 Lite's . I'm the main account holder on this contract. The other phone was given to my little brother. He constantly complains that Cell C keeps calling him for a new deal or new upgrade. He keeps telling the consultant that he is not the main account holder and that they must phone me. They keep phoning, I tried to phone Cell C , after a long wait one of the consultants answers, I explain my situation to him, he answers me with an attitude and say I must call 084 143. I cant wait to finish this contract with Cell C , because the telephone signal is worst then ever and Cell is anyway expensive. I only have 10 months left with this nightmare of signal then I'm switching back to MTN.