Try this. On your Galaxy phone under settings, go to Advanced Features>Call & Text on other devices>and instead of toggling off and on the switches, hit the three vertical dots to the right of "Call & text on other devices" which should be at the top in bold. It'll then bring up a separate smaller sub-menu with 3 options: Remove device, about Call & text on other devices, & Contact Us. Tap Remove device and follow whatever prompts come up. Turn off whatever features or switchs on your tablet that have linked your phone and tablet together. Then go back and re-sign / re-sync the phone to the tablet like you're doing it for the first time and then follow the prompts and do it on the tablet next. Making sure you're on the same Wifi network, have a buddy text and call you and return said texts and calls and you should have things work out now. I tried this now and it worked. I can't speak, however, for it wholly syncing all previously sent messages done in between that time or done while using other texting apps like if you used Google Messages for a few days or so, and then BAM, you use and switch over to Samsung Messages.