WIPING OFF CELLPHONES WITHOUT CONSENT!!!

2 weeks ago my cellphone (Samsung A5 2017) decided to stop charging... and could not go on. I then took it to Samsung Canal Walk, where they tested it and informed me that it did not charge and it would take them atleast 2 weeks to fix. So they advised me that I should take it to the Samsung Store in Century Way. Then at Century Way Store I booked it in on a Tuesday, and i was advised that Fri it would ready for collection. I called several times to follow up oh the status of the phone on Thurs n Fri morning. I was told it will be ready for collection by 11am the latest, I Samsung to collect it at 11am, and they only started working on the phone I got there which was very frustrating for me. When they were done "fixing", I turned it on and discovered that the phone was completely wiped up I had nt even been informed about it?... I asked that agent and he informed me it was the easiest way to resolve the matter which was shocking to me! As I was setting up My phone on the wifi, I overheard of the technicians speaking to the guy that seemed like a supervisor about another customer's Phone and said something like "No, its easy just to wipe out the whole phone, that customer is crazy. Why must we back up for him, its his problem mos..." It seemed at though they have one "cure"/diagnostic to every phone problem there...just wipe it out!... this really concerning for me and utterly unacceptable. I couldn't help but think that they probably did the same thing to my phone. Its one thing for Samsung to produce 2017 ****py phones with all kinds of problems but its another to just wipe them out without consent and/or proper diagnostic work instead we lose our valuable information! ??????