Ok chizzles, I reckon Childline would be better for this tbh, my parents might get a bit suspicious if they saw charged calls to Samaritans on my bill...
Want my advice? Do it while out of your house.
I phoned a helpline for homosexual teens with my gay friend a few years ago while in my house. Turns out my mum over heard and asked me about it. Wasn't the easiest thing to explain. Especially since my gay friend hadn't come out yet. Though your situation is different, I would still imagine it wouldn't be something you'd find easy to explain to your parents.