Mtn customer service useless

MTN South Africa pls explain to me how a pre paid sim card can be suspended. This is the 2nd time already. 1st time it could not be resolved so i had to do a sim swop and still it didn't work. Bought a new sim card and the 4 months down the line its suspended again???? Its daily calling with no assistance then get told go to your nearest store. Don't you think ive done all of this before