How can I deactivate Google Voice on my iPhone?

I have iPhone 5 and Verizon service. I used to have Google Voice number but I haven't used it for 3 years and its no longer active. Couple of months ago I noticed a tone every time I dial a number to call out on my cell phone. My calls would then drop after couple of minutes in conversation with the person I was calling which is beyond annoying. Went to Verizon store, they changed my sim card, which did absolutely nothing. Yesterday finally after a tone, I got an automatic message that the "Google Voice is ready to connect my call". I deleted Google Voice app from my iPhone, and its still happening. I looked for settings all over the place and I have no idea how to deactivate this unwanted feature. Any thoughts?