it is because of one out of 2 reasons:
1. maybe he was interested in you. if he was not interested in you he wouldn’t call or texting you, his attempts failed so he felt you are wasting his time and for sure nobody wants to feel rejected, so to keep his dignity he moved on and seems hooked up with another woman.
2. he was playing not that into you and you decode his calls as he want to make a relationship with you or something like that.
Actually as I can understand from your post that you didn’t give him enough attention, and he felt rejected !!
what you have to do now:
you just can not change the situation for whatever reason!
if you continuing calling him you will get desperate because of failed attempts. just move on don’t waste your time, many men out there deserve you.
by the time, you will forget him, so why not forgetting him by now ! look, if any man does not answer your calls immediately break up with him , spend your time in what makes you happy and don’t look after who is not looking after you.
Good Luck