GLOCELL HAS COMPLETELY MESSED UP MU CONTRACT AND DOUBLE BILLED ME FOR MONTHS

I have had my cell contract for almost 10-15 years. Glocell recently migrated it to Cell C but they have migrated my contract into another persons name, address and ID number, even though I still pay for it. Now no one can help get my contract back into my name because they say the ID numbers dont match. I cant get hold of anyone at Glocell and Cell C can't give me any info or change it back because I dont have the original signed contract from 15 years ago!