K. Tailoring

This is the WORST customer service I have ever received!
I handed in my evening dress to get it taken in. When I gave it in I said I didn’t need it back quickly and they had two weeks to complete it (he gave me a £5 discount wuhu!). I tried on the dress there and they put in safety pins to mark where the dress should be taken in.
When I came back on the agreed-​upon date to pick up my dress, it wasn’t ready (!) he asked if I could come back the following day, but I needed the dress that weekend so we agreed I could pick it up later in the evening. Quite annoying, but I agreed.
I picked up the dress later. When I came home and tried it on, it was way too small! They had taken it in too much and I had about 10 cm around my ribcage where I couldn’t close it !! I didn’t understand how there could be so much of a difference since they took my measurements.
I went back straight away, but they were closed. Left a voicemail on the mobile number. Didn’t hear back.
The following day (same day as my event!) I went back, tried it on. The tailor could obviously see it was too small but tried to give me excuses how it was the fabric, etc. I insisted that I needed it back that afternoon and he said I could come back in an hour. He wasn’t apologetic at all. When I came back after one and a half hours, it was still not ready! A joke at this point. I waited 30 min and tried it on only to find out that they had taken it out to the original size ie they hadn’t changed anything (!!) so they had to take it in again!
Also, despite my many complaints there was still no apology from the manager! I thought it was only fair that he gave me a discount and I even said, when they took the dress out to the original size, that I didn’t want them to re-​do it but to give me my money back. He refused!
They did the dress but it’s not at all perfect. I found it so appealing the behavior and attitude in that shop! I can understand that sometimes unexpected things happen, but I find it very unfair that I had to suffer for this! The tailor could at least have given me a discount for this extremely poor behavior and experience! I am definitely NEVER going back to them again! Worst service ever!