Unhappy tenant

I had a rental contract with Chase Everit. I moved out on the 30th November 2020 and according the contract I was to get my deposit back into my bank account between 7 and 21 days up to date no money. I have being renting from them for 6 years. I am waiting for my deposit including interest. All I am told I will get my deposit on the 4th of January and after refering the matter to Hello Peter I received a whatsapp text that the money will be paid into my account the following day, regrettably up to now no money was paid to me which is due to me. Why must I fight for money that is rightfully mine. This is so unacceptable this behaviour treating me like a beggar for my own money. Even the manager promised me I would get my money but nothing. This is a blatant breach of contract. What can I do to get my money back.