It's Taking too much time for Synchrnizing messages?

Hi,

I am using Nokia phone of AT&T from USA. It is working but while sending messages it is taking atleast 2-3 minutes to go and when I receive any message.

It will take atleast 5 minutes to Synchronize.............why it is taking so much time?
If I need to send multiple messages from same number then I have to wait for 2-3 minutes after sending each message. Please suggest me why it is so slow.

Thanks,