MTN **** service provided

This is the second time for the month that our service has been suspended.After we pay our account promptly every month.The service provider still has my device after I only had it for 3 weeks it going on 4 months now and I still don't have my phone back.After they promised high and low they will sort my phone out they rather gave me a earphones and than told me after a few months sorry we won't be able to assist you .........