Phone in for repairs, lost and they want me to pay 11k for reapair

I had bought A phone, of which i was paying over 1k a month, the phone gave problems with the charging port, sent the phone back for repairs and the bought it back, within a week, the phone gave the same problem. I took it back they sent it for repairs again, i was told to pay 11K, i decided to pay my contract out and they still have the phone, because i cnt pay 11k to fix a phone, they accuse me of dropping it, they say i should pay 11k. They still have my phone and i went took another contract with thwm, and i am not paying it. The reason for that is they do not even know, where the phone that was in for repairs is