Battery repair done 3 times STILL have same prob

In mid November I took my iphone6 to Ifix to have it sorted as the battery life was only lasting 2-3 hours. We were told to leave the phone there as it was almost their closing time. A friend brought to phone to me a week later after the repair as I live in Burgersfort 148km away, it never even switched on, wouldn't charge either.( should this not have been tested) again phone was taken back the very next day and again I was told it must be a faulty battery in( again was it not supposed to be tested by the pros) 2 weeks later I got my phone back again, with another friend who came this way.The phone was charging and coming on but after taking it off charge at 100% it dies within 3 hours which IS NOT NORMAL. We took the phone back ourselves 2 weeks later and was told AGAIN the battery needs replacing. When getting the phone on 100% we walked upstairs, within 15min the battery life had dropped to 78% so I took it back and was told to take it home and let it die and charge up and bring it back if it's not right ? I explained the distance I live and that the phone has been back 3 times and I was told it has to die and charge up 5 times before it will work which is the biggest nonsense