DS is 16. He wants me to buy him some online tv service which will allow him to watch WWE wrestling. Basically because his friends have it and he thinks he should 
I have said no. Various reasons:
DS is overweight but wants to get fit, so I offered to sign him up to my gym, and pay the first month. He never went, though kept saying he would, and would pay me back. I eventually cancelled it at Xmas, he's not paid a penny.
He already spends a lot of/ too much time playing Xbox and on Skype or Snapchat or Twitter to his friends. He is doing AS levels and has already had a ticking off twice from his school for getting behind with work.
He doesn't do much round the house, makes a mess, and is often pretty rude. He doesn't get up unless I spend 15 mins shouting at him (and run him a bath) every morning.
So generally I am not that well disposed to him atm. And I don't want him having more excuse to be online til all hours.
He says this is v unfair, and I am bu.
I've told him to ask his dad instead. Apparently he has, but his dad (my ex) said he didn't see why he should do it as he already pays DS's xbox Live account, and to ask me.