MTN erroneously upgrades wrong number and unable to correct their error!

I have been an MTN Customer since c.1996 and using the same number since. I upgraded my line on 3 June 2022. Only to discover the incorrect line had been upgraded. The Contract I signed clearly states the correct number. MTN Howard Centre admitted to the error. However, I was told there is nothing they can do about it. The matter was escalated to team leaders and still nothing to date. Neither the store nor the call centre is able to solve this issue. Poor service, poor systems... what next - lawyers to get MTN's attention!!!!