Specsavers Customer Communication Assistant interview questions

I applied online didn’t hear back for over a month. I was invited to an interview with the Asmin Manager, but when I got to the interview on the day it turned out she was on holiday so I had my interview with the store manager. It lasted around 40 minutes mainly talking about my past experiences. I was then invited to a trial shift about a week later. I was told it would last two and a half hours but when I arrived on the day I was told it would only be an hour and a half as the Admin Manager had to leave early for an appointment (I thought this was unfair as other people would have had an extra hour). I was explained general day-to-day activities, introduced to the team and just watched the Manager do some tasks, and asked to help on a couple of simple tasks such as matching up contact lens orders to the customers they were for. At the end of the trial shift the Admin Manager spoke to me about rate of pay and said I could start on a specific date (after a pre-booked holiday week) and that she would contact me in the next week to arrange everything properly. A week later I still hadn’t heard anything so I called her and asked what was going on, to which she replied that she had contacted head office to send me my offer email but they must not have contacted me, so she would ask them again to. This was on a Thursday, and I didn’t hear anything until the following Monday, when I got an email saying I DIDN’T get the job. So I rang the store as I had already handed my notice in at my current job, and they said the Admin Manager had the day off that day and they would try and find out what was going on. About an hour later I got a call back from the Store Manager apologising and saying the email was correct and I didn’t get the job. I explained to her my situation that the Admin Manager told me after the trial shift that I could start on the specific date a couple of weeks later, and she said that she shouldn’t have offered me anything face-to-face, they only make offers through email. So now I have been left unemployed after all of this. I asked the Store Manager for someone higher up that I could make a formal complaint to; she gave me an email address and told me to email them with my phone number. So I wrote an email explaining the situation and giving them my phone number asking to call me back; a week has passed now and I have heard nothing. Highly unprofessional.