Poor service concerning my cellphone

I bought a phone last year November 2018, name of the phone was mobicel before three months it gives me a problem, i return it back to the store and make a top up, i then took Hisense phone it also give me the same problem of freezing,switching itself off, i was given three new Hisense cell phone in a period of 7 months the last time i submit my to the store it was mid June 2018 ever since i bought that phone i never enjoy using it, even now i dont have the phone is still at store everytime when i talk to them through E.mail they took me from pillar to post Proof of purchase# ********** 2