First of all: I wouldn't recommend Belize at all, unless you have done a lot of research, consulted with advisors (lawyers, tax advisers), and definitely concluded that it isn't a terrible choice. Make sure you've done your homework before sinking an entire business into a Belize company.
If you are confident that Belize is a good choice for you, make sure you work with a service provider that is locally licensed. Only work with an agent/reseller if they add a clear benefit over going directly to the source (such as legal advice, tax advice, better banking network).
You can find a list here:
Licence Activities | Belize Financial License Activities
On that list are some reputable/well-known service providers such as Vistra, Icaza, and Quijano, and some old foxes like BOSL (Belize Offshore Services Limited), Morgan & Morgan, ICS (Belize Offshore), and AP Intertrust.