Entity boundaryRegion vs. Telephone Area
These pages cover the five complete BTCL geographic NDCs, not universal city codes. Other PSTN and IP-telephony operators combine their own network prefixes with the same zone structure and therefore use different NDCs. Each zone spans many districts, some administrative divisions cross numbering-zone boundaries, and migration from older local formats means a published address or business may still show a legacy number.
A code listed beside a city reflects a featured numbering association; it does not assert that every community in Mymensingh Division uses that code or that the code stops at the administrative border.