Cell C database incorrect

Despite being customers for 15 years and having an excellent credit rating according to the same credit report as CellC uses, we are denied upgrades as CellC says our credit record is not good. The problem is no one will engage with us to explain the CellC side so even though we send through our credit record and called the call centre numerous times . This has been going on for 6 months. We have been offered upgrades but they never arrive and then we are told our credit is bad. This is so frustrating but we are trying to avoid porting our numbers and changing service providers but are now left with no option.