I'm from San Diego and a customer of T-mobile since 2009. Seeing these issues of not receiving calls and texts for a while now even with signal showing 3-4 bars. Sometimes I'm able to make my device receive calls by putting device in airplane mode, wait for few seconds and out of airplane mode. Definitely need a proper solution from T-mobile for this. I'm using an unlocked Sony Xperia XZ.
Sounds like a difficult problem not being able to call or receive messages in a timely manner!
I suspect the APN settings are not properly addressed. Want to help me with making sure your device's APN settings are set properly?
Use this link to set the APN for your Sony Xperia XZ.
Please update me and let me know what happened!
Manage your T-Mobile account