Wireless General Device Discussion/Support

[#1]

I have noticed lately that when I text someone, my phone says that it has been delivered, but sometimes it has in fact not reached the person in question. This is REALLY disturbing because I never know when this happens because for me it looks like it has been delivered!

Please tell me how to fix this!

[#2]

Does it have something to do with the Text message Center Adress?

the number typed in there right now is +{Personal content removed for your safety}

I live in Nor Cal

Should I use another number? Please help me Because this really sucks..