NAL,
But can assure you, it’s not someone from the telecom operator. It’s your fault, she had access to your Data and phone.
1) She installed a spyware app on your Android phone.
Remedy – Clean out your phone with the help of an IT guy or Just change the phone.
2) Synced your mail account to another device.
Remedy – Check your mail sync and unsync your call logs or any automatic data sharing to mail.
3) Easiest – One can easily access call logs using telecom apps. My colleague uses My Jio app to check call details.
Remedy – Just login with another device and remove the app from all devices.