Heya I need some advice from people who know what they are on about.

So Ive worked at ASDA for about 13 months. The contract I signed was for 22.5 hours a week. Since starting ive only ever done 16 hours a week. When I started I asked every shift for about 8 weeks what days I should coome in and work due to starting around christmas time I was in solid for about 4 weeks. After the christmas period I continued to ask, in my year there weve gone through 3 mamangers and 2 human resrouce people. Ive asked them all multiple times can we sort my hours all saying they will speak to the higher up. I still havent worked my full 22.5 hours a week and it really would help with my current finacial situation if I was to have the extra hours.
So my question is do I have a right to some form of comepsation for hours lost? its caused me great stress and anxiety dealing with debt collectors while trying to sort this. How would I go about getting a tribunal?