New 1GB MTN update for N200 has been uninstalled ... once you exceed the subscription limit, you can subscribe for weeks. I think this is done to discourage people from registering.
However, you can always do to re-qualify for the offer without much stress.
How to be Eligible for MTN 1GB for N200
Don’t activate any data plan on that sim for 3 – 4 weeks, you can be using it for calls but don’t activate data on it and it will be eligible again. I’ve tried this time without number and it worked perfectly for me. This is the reason why you should have more than one MTN SIM.