PMP Recruitment complaint: Lied to and never shown any respect

Been told by Mohammed with pmp, who manages gxo widnes, that I am entitled to extra pay on the Easter bank holidays. Come to my payday and I’ve been paid normal rate, I’ve rang him and asked him countless times to fix the issue he didn’t seem to care just telling me time and time again he will let me know. It’s been nearly 2 weeks since I worked the bank holiday day and he’s only just told me that I’m not entitled to it. When I told him I feel he has no respect for me and that I want to speak to somebody else he laughed under his breath at me. He then told me he’ll send me a text with an email I can contact, which he never did so I rang him numerous times after that to which he didn’t answer. I’m being shown no respect by him, I have to ask him countless times to do something simple. There’s been plenty of times I’ve booked and ed my shifts with him but when I show up to work I’m being sent home because he hasn’t put me down. It’s disgusting how I’m being treated and how everyone else is, there’s plenty of people in the warehouse I’ve spoke to who feel the same way I do.