Pathetic service from incredible connection more like disgusting connection

This company claims to be the best but I have got nothing but terrible service from them firstly my phone kept switching off after having it under 3 months yet I did not plug not a thing into it besides connection to a charger. Secondly which brand new phone as a software issue after 3 months. Thirdly I first approached them about it and a service agent has the nerve to tell I cannot bring it back to be sorted out. Fourthly I go to the store they take my phone in and tell me up to 21 working days and now it's way over the time that was given when I do call the store the technician tells me there is no communication about the phone the managers aren't communicating with them and the courier service is delayed. That is not my problem I either want a new device or something because this is rediculous I have lost and used alot of money with these people.