Just leave. You don't need to even answer your phone, and don't need to change your number. There is nothing he can do. And he definitely won't 'kill you'. I have left loads of parlours this way...sometimes on good terms, sometimes on bad terms. It's very simple actually...you're making this out to be harder than it is. I have also been threatened. But they NEVER follow through....because they would get in such deep shit if they did and lose their entire business, which is too valuable to them. They care more about their busniess and money than they care about you. So don't be scared to just walk out. they might ring you once or twice, but trust me they get bored easy and move on. Good luck.

I need to add here that you should not take anti biotics unless given to you for an infection at that time. They are not to be messed about with and taken just in case you have an infection. If you take them unnecessarily you could become immune to them.x

Just a note on the infection front.

If you suspect you've slept with someone riddled with Chlamydia, do not take the antibiotics the following day or even a few days after.

This isn't really how infections and antibiotics work. The delay which you're thinking of is the time between encountering the bacteria and the bacterial load growing to the point where the immune system's response is detectable in a screening. Antibiotics are frequently administered pre-emptively for various kinds of infections and exposures.

However, I'll second the opinion that you shouldn't be taking anything you haven't been specifically prescribed. For one thing, not all antibiotics work on all infections, and STIs generally require specific drugs because they've become resistant to a lot of treatments (this applies especially to gonorrhoea, but chlamydia has also been recently been found to be exhibiting resistance.)