Welcome to Android Central! First of all, the REVVL is a T-Mobile branded phone made by TCL (not Motorola).
Second, have you looked at the Data Usage section of your system settings to see which apps or services are using the most data?
Third, how do you know texts are being sent and received on your account (but presumably not visible to you)? Have you discussed this specific question with your carrier? I know you said your "phone company isn't any help", but what exactly did you discuss with them?
Fourth, where do you see this IPv6 address, and why are you worried about it?
Fifth, your Google Activity shows when apps ping your Google account to refresh data. This happens frequently with many apps at all times of the day, even if you're not actively using them. It's normal.