LG Electronics — Rusting inside microwave

Inside the microoven rusted within 3 months which purchased from reliance digital, Magneto Mall, Raipur and now now relianace digital and lg electronics bhilai insisting me to repair it. and we ask them to replace the same but they deny to do it by the both of the party. if it is rusted within 3 months of purchase then what will happen after one year ? for that reason i ask them to give me the written assurence for the futre but non of the above people doing the same. they are also reluctent to change the same. here i am giving all contact numbers of concerned people. ([protected] / Ms. Aarti / Reliance Digital, Raipur) ([protected] & [protected] / Mr. Salil Kumar / LG Service)