Does your Sipgate service provide Caller-ID with name service? If you use a different softphone, do you see the caller's name?
Many VoIP services will offer free Caller-ID services, but will not provide Caller Names.
This is due to the fact that the service provider usually has to pay for access to a CNAM database (for Caller Name Lookups), which is typically charged on a pay-per-call basis.
In order to save money, many providers don't offer name services or charge extra for them.
On a separate note, Caller-ID with name service is only available to North American subscribers, most other countries do not include the Name in the local Caller-ID standard.