Please help really desperate!!!?

i'm being harred by some one who has got hold of my mobile no, i've got theres 2 but they will not answer it, they have now managed to get my partners number and are sending him nasty text, i've tryed that reverse number look up but there mostly from stateside or the few that are uk are expensive( there stalking me i don't wanna pay) ther starting to get nasty now any advice would be really appreciate it as i really don't know what to do