TOTALLY ANNOYED

I've been with MTN as long as I can remember. I'm totally disgusted and so disappointed. I recently upgraded and after saving on my airtime (400+min) I noticed yesterday that my minutes and sms'e now stands on 000. How can I forfeit minutes I earned on a previous package???? This is not fair and not how it should work!!! This was part of my previous package. I want an ANSWER ASAP and my minutes back!! I've have a connecting number to my *** (deal done over the phone with MTN) and up untill today never received a sim card for this. How do I load extra airtime etc onto this number without a sim ????? I'm a pensioner and not sure how these things work.