Understand the issue
Outdoor coverage maps do not describe every interior space. Concrete, metal and coated glass can weaken signals, while interior distance and neighboring structures change the path from a carrier site.
What to consider
Start by separating coverage from capacity. A weak signal in an empty interior room suggests a different investigation from slow service only during busy periods. Compare carriers, devices, floors and times of day.
Make the next step useful
Log the exact location, time, carrier, device and symptom. A scoped RF survey can map the issue and help determine whether an antenna system, small cell, appropriate booster or another intervention is justified.