Employment Tribunal

I got offered and accepted a part time job. I worked 1 day, then I was told to not come to work as he was going on holiday for 2 weeks. I then went back to work for another week. I only got paid for the days I worked. Then I had a text to say don't come to work as I need the desk, then another text the same week to say I'm only working until lunch on my other day. All this time I was asking about holidays, contract, etc nothing appeared. I also questioned him about my hours and that this wasn't what we agreed. He then said sorry things have changed and I will let you know weekly if I need you to work. I thought about it, told him I wasn't happy with that arrangement and I wanted paying for the days he told me not to work. He told me no he wasn't paying me as I'd not been there 3 months. I contacted acas for early conciliation but when they called and said who they were, he put the phone straight down. Now I'm going to tribunal. Do you have any advise. The acas lady said it is very straight forward and I could go on my own. I have kept all the text messages from him and he paid me straight into my bank so he can't say I've not worked for him. It's not fair he shouldn't be allowed to get away with that.