There are several reasons why you may experience weak or no signal inside a shopping mall:
Distance from cell towers:
Shopping malls are often located in busy commercial areas, and the buildings surrounding them can block or weaken cellular signals. If the shopping mall is located far away from cell towers, it may be difficult to get a strong signal inside the mall.
Shopping malls are often made of thick concrete and steel structures, which can interfere with radio waves and weaken the cellular signal.
Shopping malls can be very busy with many people using their mobile devices at the same time, which can overload cellular networks and cause signal congestion.
Interference from other devices:
In addition to mobile devices, shopping malls have many electronic devices such as Wi-Fi routers, security cameras, and Bluetooth devices that can interfere with cellular signals.
To improve signal strength inside a shopping mall, some buildings install signal boosters or repeaters that amplify the cellular signal within the building. You can also try moving closer to a window or door to get a better signal, or using Wi-Fi calling if your phone and carrier support it. Finally, if you consistently experience poor signal strength in a shopping mall, you may want to consider switching to a carrier with better coverage in that area.