I managed to configure my voipcheap account to work with Ekiga.
Though the phone numbers that u have to call look a bit awkward (sip:<phoneNumber>@sip.voipcheap.com), but it works.
I basically love the fact that I reduced another reason to boot into windows. Loving Ubuntu every minute...
Here's some documentation on How to Use Ekiga
Ekiga - Community Ubuntu Documentation
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