Phone still broken after repair

I just collected my phone from your Walk In Centre in Buccleuh, and by the time I got home the issue occurred again. The phone still switches off and I cannot switch it back on again unless connecting to a charger. Not even an hour since collecting it. There is a problem with this Sony Xperia M5 and I have seen lots of complaints about it. I am already paying for this new contract and insurance for a phone I cannot use. Not to speak of the petrol I have to drive out to your Repair Centre!!! Please contact me urgently. I am leaving on holiday tomorrow, now with a broken phone? I tried to reach you via your Call Centre but they say they cannot contact you. <br> <br> This is really pathetic service. The main reason I upgraded my contract was for the device. I am not happy to be paying for something I cannot use!