Should I quit my job?

I'm 19 and in London now for the summer, I basically took the first job that I could get and it was a telesales job. I'm selling online packages from BT to previous customers and it kind of sucks. I don't even get commission like I thought I would I just get 7 pounds an hour. I only get like a fiver for every sale after my third one but that rarely happens for me. Also the hours are 1 - 9pm and it eats up my whole day. It's just sitting there with a headset on selling the same **** to people who don't want it. I'd like to do something more fun like a bartender position but I have no experience so I'm worried that if I quit this job I'll end up as like a kitchen assistant or worse not be able to find another job. I mean it sucks but its good experience, I'd be a bit embarrassed to leave it for something less respectable. Also I took a 4 day training course and I don't get paid for that until after a month but I've been on the phones for 2 weeks and I think its not worthwhile. I can tell my agency on the day I want to quit since they've got a fast in fast out policy but I won't be able to get my job back. What should I do? Do you think I can find another job?