my old iphone 4 was stolen so I got a new iphone, however i keep getting random contacts appear that I do not know and mine keep going missing?

Hi

A few months ago my iphone was stolen out of my car, i did not have the IMEI number so I had to block the SIM etc... I then went to a new provider and transfered my old number accross and started on a new Iphone.

I changed all my passwords etc as you would normally do however since then something odd has been happening.

Quite reguarly now I get random numbers appear in my contacts assigned to names (generally in 0092 area code) and occasionally my contacts are deleted. I assume that somehow they are being seen together.

Has this happened to anyone in the past? and how can I fix this as I am slightly worried what they can actually see.....