SWOLLEN BATTERY

i took my phone in for repairs at mtn cause the battery had swelled as if it wants to explode and the phone was now reduced to a landline as i couldnt use it for long when it is out of the charger. it being the first 4 months since i bought the device i was not expected any issues. Estimated charge was placed at 250 rand. now i get a quotation from mtn saying its going to cost 4880 rand. when i ask why they say cause the screen is cracked . i have been insisting i dont want the screen repaired i want the battery changed cause clearly its a manufacturer defect. Now Zandi says i should come and collect my phone. really not happy