Wont repair my phone- Warranty rule unfair

Im from the Midrand Repair centre to book my phone for them to fix the charging port, before they did anything they just opened the phone and told me it has liquid damage.<br> i told them i have never immersed the phone in any liquid, their response that liquid damage can come even if its steam at the kitchen or if its in my pocket. My complain is the Warranty rule are so unfair. they are declaring liquid damage because of pink mark reasons. MTN is actually cheating their customers my this ridiculous warranty rules. No one explained to me that i must avoid steam , i must never answer my phone in the kitchen.How do i know that the pink mark was there on purchase ?? I feel i was sold a faulty phone , the charging port is faulty in less than 2 months, they say its physical damage. Im so thinking of cancelling since this is the 2nd phone in less than 6month ,Im on a BIS contract & Im paying not using the service. im a long service customer and MTN is failing me . I have 16 months left on the contract that i will be paying & i wont have a phone to use the BIS. I think its time i look for a better home with your competors as i feel cheated