DISGUSTING SERVICE REGARDING UPGRADES

In 2021 I completed my debt review and got all my clearance certificates. At that time Cell C received the paperwork and I was able to do my upgrade. Now they will not do my upgrades (2 contracts) as they have said that I am black listed. Not once have I missed payment nor do they fall under debt review. I have been with Cell C since they started but this service is totally unacceptable! What is it going to take to get my upgrades which is owing to me? I have sent all my clearance certificates to them buy they cannot hand me a senior manager to talk to - they only want me to deal through the call centre and they don't even have contact details or names. Absolutely disgusting this service!