Dude.....she probably changed her number coz u called her a lot and she must be afraid that.....hey I am not trying to be pessimist here....but just an assumptions......
If she has not chaged her number, she might be afraid to take your calls coz she might spill the beans by saying that she likes you too.....another assumptions.....
If all hell freezes...than.....she might have got another got BF and she doesn't care about you no more and ignores ur call saying that,"just another random guy" (please don't take offense for saying random guy....u might be great.....i don't know u...)...third assumptions.....
Last but not the least........she might be waiting for u tell her that u have fallen head over heels for her......fourth and last assumptions..........
Did you say...she has a BF.....did u ever meet him? or is it jus a "fake" BF?
Life has full of suprises.....don't hang onto one.....let another come along.....
Peace out...
Ram Parsad