can you advise where there is a Dtac office in pattaya? Is there one in that big shopping centre central festival?

If I get them to de-register or cancel a dtac sim card, does it mean that if someone then tries to text me (from within thailand or abroad) they will get a message advising that it did not work?

thanks

I know for sure there is one on 2nd floor of bic c extra work n central (klang) road.