Has your site been upgraded? Because B4/B66 performs worse on the new Nokia AAFIA Massive MIMO equipment in Texas. Before the upgrades, T-Mobile physically split sectors for B2/4/66 and coverage+performance was pretty impressive. B4/66 coverage was actually very close to that of B2 (even outperforming it in some instances).
Now that my local tower has been upgraded, I still receive B12 and B2 from it. But my B4/66 now comes from a different neighboring tower as my home tower's B4/66 is drowned out. As you can imagine, I no longer get the same peak speeds as before since CA doesn't play nice with bands coming from different towers. Even the newly added B41 has a better reach than B4/66 (getting 80+ mbps downloads on B41+B41, T-Mobile just needs to optimize load balancing as B41 thresholds seem very conservative).
I don't have the "hearing me" problem, but I bet it's network related..... I just rarely get calls and texts when people call me or text me. Telemarketers seem to always get through but never the important calls. The New T-mobile sucks just as hard as the Old Sprint.