strange phone number!

Hi,

I got a strange question to ask, (for UK ppl only).I'am receiving this strange number 01872 260795, or it always starts with 018722..which displays on my phone "its a new way to make prank calls i guess" (nobody answers btw) and when i try to call the number back, its always busy!
Nebody come across with these kinda calls?, if anybody knows about those kinda call or knows how to make this call pls let me know, i would really appreciate that. coz i fink i know who the caller is but i need to learn how she does it! lol.