NO HELP, NO SERVICE, NO FEEDBACK

I GAVE MY PHONE IN ON 25/05/2015 AT MTN. THE SIMREADER WASNT WORKING. ITS NOW MORE THAN 5MONTHS LATER AND THE PHONE IS STILL NOT WORKING. NOW THEY SAY THE PHONE IS BLACKLISTED AND THEY CANT DO ANYTHING. WHEN THE PHONE WAS IN THE SHOP AT ON STAGE THEY ALSO PHONED AND THEN SAID NOTHING WAS WRONG. SO SOMEWHERE WITH THEM SENDING THE PHONE UP AND DOWN THE PHONE WAS BLACKLISTED. NOW THEY SAY ITS MY PROBLEM, THE PHOEN IS STILL UNDER GUARANTEE AND THIS HAPPENED WHILE THEY HAD IT. BUT IM THE ONE THAT MUST PAY FORM SOMETHING I DONT HAVE, THIS IS MY THIRD REPORT AND STILL NOBODY HAS ASSISTED ME.