ok firstly I need some details

Who is your service provider?
What handset?
Is your phone branded? (ie does it have service provider specific stuff on it?)
Has SEUS worked in the past for you?
What is your current firmware?
What is your CID number?

As stated previously the service providers do not always have the most up to date firmware available for the unbranded phone as they use specific network branded firmware, which may not be released for that SP yet.

If youre using an older CID 36 handset or CID 49 you may be able to update, debrand yourself using available software such as gflash, FAR and xs++ etc. Gflash works for K750 and W800 CID 36 phones. As does FAR. There are methods for using FAR with CID 49 phones too. Have a hunt on the forum, and other SE forums.

hope this is helpful. if it is please hit the thanks button.