Hi Bill:
You can transfer a Google Voice phone number from one Google (Gmail) account to another one. The target account cannot already have its own Google Voice phone number.
Only the Google Voice phone number will transfer over. All of your saved call and text history, voicemail messages, settings and linked forwarding phone numbers will stay on the transfer-from account. You'd have to manually delete the linked forwarding phone numbers off of the transfer-from account, and then manually add them to the transfer-to account. You'll need to record a new voicemail greeting and customize the Google Voice settings if you wish, on the new account.
Number transfers are free, and they happen immediately. See:
https://support.google.com/voice/answer/1065667#googlexferOBiTALK devices authenticate to the Google/Gmail account, not to the telephone number, so you will need to click on the Google Voice SP in the OBiTALK dashboard, and then get to the window where you can change the Gmail address it is using.