On and Off??

Hopefully this will help... My husband has a contract for more than 10 years... 3 months ago he keeps on receiving sms and got cut off for outstanding payment.. I've send numerous emails to customer care, visit a branch and constantly communicating with mtn on messenger...Only when we think the query is resolved, we actually got messages saying the query is resolved.. He received the outstanding bill sms...how can we proof that the account is up to date as proof of payments was also send on numerous times...