Samsung galaxy sII not receiving texts!?

Hi,

I just got my phone 3 weeks ago. Samsung galaxy sII, it is on the rogers network. The problem I'm having is that for the last couple of days, I am not receiving texts, but my friends have been getting my texts. Other times I will get their texts after a delay, eg. several hrs after. I have no problem sending texts. Does anyone know what I can do to fix it? Is it a network problem or is it just my phone?