cellular data is not working correctly

Good evening, please tell me I have such a problem. Firmware version 13.6.1 sometimes a strange thing happens to the phone, the phone shows that mobile data is on and there is excellent coverage, it also shows the LTE icon, but in fact the Internet drops out and stops working .. This problem is solved only by rebooting the phone or by turning on and off the mode on the plane, tell me what to do ???? ( cellular data is not working correctly