It sounds like you didn't pay attention when you set up the phone, and you don't understand the concept of
inbound calls vs.
outbound calls. You can configure the OBiTALK device (IP phone) to use a desired SP as the default for
outbound calls when you pick up the handset or press the speaker button to place a call. That is controlled on your OBiTALK device configuration page, by clicking on the desired SPx and setting it as the default for outbound calls. To call out via one of the other SPs, press its line button on the phone.
However: when an
inbound call rings, THAT SP becomes the one that will be answered when you pick up the handset or press the speakerphone button.
Your issue is that you configured Google Voice to ring multiple destinations at once.
If you incorrectly set up Google Voice, then you now have Google Voice calls forwarding to both your native Google Voice service provider, and to Callcentric, at the same time, thus making a mess when you receive a call.
Sign into your Google Voice settings page:
https://voice.google.com/settingsScroll down to the
Calls section. Find the OBiTALK device you added. Toggle the switch to the right OFF (grey, not green). There should also be an entry for your Callcentric number, that that should be toggled ON (green, not grey). You can still make outbound calls using the Google Voice SP on the phone, but that SP won't ring on inbound calls.
This will stop inbound calls from being sent to the Google Voice SP on your phone, and instead, you will only receive them via the chosen Callcentric number.
I don't understand why you have a second SIP service provider configured, but
do not forward the Google Voice calls to both SPs, or again, you will have redundant, simultaneous ringing.