JS -
the phone thing is a HUGE POSITIVE

When the OW called my H on his cell phone after we had started getting back together, he took out the battery and broke the phone! He just didn't want her to call him or for him to be tempted by her. He was still pretty confused at that time, but that was a real turning point.

I suspect your wife getting rid of the phone is either:
A) - an attempt to rid herself of phone calls from OM or other undesirable influences

B) - a peace offering to you in an attempt to become more trustworthy.

Sharing a plan with you means you will see the bills and the phone logs - so that's a big step for her to take Act happy about it, take her out to get a new plan with a fun new phone, send her cute text messages on it!

Ellie