i phone

My i phone 7 was sent in for a new battery The day after i received the phone back the phone went haywire i could all of a sudden not hear incoming calls and vise a versa. When i took the phone back to an i store to complain, i was told for the first time that the phone had failed an audio diagnosis. The manager of the store suggested that they take the phone in again to do a diagnosis again. I was then told the phone had failed an audio diagnosis. I reiterate the phone was in perfect working order except for the battery life being poor. I was then given a quote of R 6,536.14 inc. Vat. to repair the phone. When i complained about this, insisting that the phone was in perfect working order prior to their service centre getting hold of it. I was told the phone was out of warranty. Their attitude is "take it or leave it" i feel bul**** by i store and believe their service centre damaged the phone.