tracking and eavesdropping through cell phone

My fiance's ex is a hacker. For over a year now, he has been somehow eavesdropping on us as well as tracking her movements. It's been reported to authorities but seems nobody knows what to do and I need to proof more so than witnesses. Is there a way to check all the lines on my account to see if this is happening through my cell phones? Should I hire a hacker to assist me with this or is it something that can be found out easily? My tech skills are around a 6 out of 10. 🙂 We have replaced all the devices with new ones along with new phone numbers and new applie ID where applicable, didn't transfer info between phones, and it seems that he is still able to do this. Any guidance or assistance is appreciated. Thanks

Re: tracking and eavesdropping through cell phone
Specialist - Level 2

He would have had to  get a hold of the phone and install some kind of tracking software I think.  Maybe you need a PI to track him.