Porting back to mtn

My name is Phumla I've ported my number from mtn to cell nd it was successful. I enjoyed their service. Now I decided to port back to mtn, a lady works for mtn helped me with the process and I received porting messages on my old cell c sim card. The problem is i cannot access my new mtn sim it keep on saying " please visit the nesrest dealer to RICA by providing the subscriber information " which I did take my i.d and proof of resedance to rica my mtn sim the lady told me that sim is already ricad and then I phoned mtn and spoke to one of their consultants, she told that my new mtn sim has to be de-registerd and re-registerd in order to proceed the porting . I went to that lady who did the porting for me she told me it is impossible to de-register and re-register . I can't afford to loose this number ( ********** 034) which I'm porting from.