iPhone in working order

On 21 August 2017 I handed my iPhone 5S in at weFix Eastgate branch to have the battery replaced. The attendant checked that all was in order and I collected the phone that afternoon. On examining the phone at home I noticed a little bubble on my screen which was NEVER there! On Wednesday the touch screen worked now and then. I reported this and they said I should bring it in which I did today. They now advise me that the technician noticed a crack on the LCD! This phone was in perfect condition when I handed it in except that the battery was giving me problems. Their service is shocking and obviously they want to pass the buck onto me. I am not accepting this and will never use their services ever again.