Lately i've been having call quality issues with my new IPhone XS. The caller's voice would sound distorted/robotic. Other times their voice would fade into the background. I've tried every scenerio to possibly fix the problem. From switching 3 phone cases, toggled between having noise cancellation on/off, toggled between having cellular LTE voice & data/data only and reset network settings multiple times. I do have IOS 12.1 already installed and still no luck. Is this a hardware issue? Network issue? Has been very frustation to decipher every phone call conversation.