Son Bullied In Prison - From A Worried Mum

I am a Mum and my son is in prison. He has no idea how much I am struggling both emotionally and financially. He is demanding money from me and demanding clothes and trainers. I think he is being bullied in prison because I visited him last week and he wasn't wearing the trainers I bought him nearly 5 weeks ago. I asked him where they were and he said that the prison hasn't given them him yet which I find hard to believe 5 weeks down the line. He got in with the wrong crowd but I am not making excuses because he has his own mind but even so, he was a good lad and a shy one that's why I think he is being bullied because he isn't a strong lad. The money I have been sending him obviously hasn't been spent on phone credit because I haven't heard from him for 4 days but did get a letter off him the other day. I just don't know what to do because I know the prison won't talk to me and give me any information. At my wits end!!!!