How do I check the call?

pu1. The call history is possible, but the call content is not possible.
Voice data is encrypted wireless data, so even with current technology, you can't see the contents

2017-11-10

OK

pu2. The call history is managed by the carrier, but it won't be possible to get the call details.
If you want to save the call, you have a lot of data, and now you have to decrypt the encrypted data, because there is a high risk of hacking.
The carrier doesn't have to do such a complicated job.

2017-11-10

OK