Mtn contract department_ not treating customers fairly

Hi... I would like report a bad customer experience , well I am on mtn contract cell phone, so since the start of the Covid19 the mtn stores were closed and I haven't received anything communication with the payment option not sure if it's because my Sim card was deactivated since from then. So sometime last week I got an email from their debt collectors indicating that my account is being handed over so I should make immediate payment,i did settle my account and contacted Mtn to reactivate my Sim with no success. And my issue is mtn is not treating their customers fairly as they could have notified me before taking further actions, now I did settle the amount but I am not getting assisted.