Why can’t I use the data I bought on my mtn line

Please how can I change my bonus to my main data plans how can I use my data plans

I haven’t been using my MTN line to make calls or send msg for the past 2 years and since last month I noticed that I cant make calls , receive calls and receive messages...

I can't check my balance or even use the data I just got because my mtn line keeps sending me the same massage that my line has been temporarily blocked, please I need a way to...