WRONG UPGRADE

I HAVE UPGRADED WITH MTN IN AUGUST 2020 ,DURING MY UPGRADE I HAVE INFORMED A LADY WHO CALLED THAT I NEED A CELLPHONE WITH DUAL SIM.SHE AGREED THAT SHE WILL SEND ME THE PHONE WITH DUAL SIM.I RECIEVED THAT PHONE ONLY TO FIND OUT THAT IT IS NOT THE ONE THAT WE AGREED ABOUT.I CALLED MTN ,AND THEY TOLD ME TO RETURN THE PHONE TO THE NEAREST BRANCH .I HAVE DONE THAT AND THEY TOLD ME THAT I HAVE UPGRADED UNDER THE COMPANY CALLED MONDO,SO I MUST LIASE WITH THEM AFTER THAT.I HAVE BEEN CALLING MONDO AND THEY ARE TAKING ME FROM PILLAR TO CORNER WITHOUT ANY HELP.I AM CURRENTLY PAYING FOR THE PHONE THAT I AM NOT IN POSITION WITH.MTN/MONDO PLEASE STOP DEDUCTING MY MONEY.