I'm having a wired issue with the mobile data on my phone (OnePlus 5T). The data signal (4G+/HSPA+ symbol on the signal bar) drops from time to time (one or two times every day), once the signal is gone I cannot use mobile data but normal phone call works just fine. I tried to turn the mobile data off, wait for few minutes and turn it back on, it didn't help. However, a simple reboot will fix the problem. Just for the reference, the mobile data for my T-Mobile SIM works just fine.