Subscribers of number series-725 under Khilgaon Telephone Exchange will be switched into 8-digit format under series-4721.
The change will begin gradually from Dec 17.
Bangladesh Telecommunications Company Limited (BTCL) General Manager (PR & Publications) Meer Morshed confirmed the matter.
The subscribers will be informed their new numbers while the changes are made, he said.
The subscribers also can call 16402 (BTCL Call Center) or 02-55120010, 02-47211177 during office hours, to know about number change.
They may also visit BTCL website (www.btcl.com.bd) to see the lists of their old and updated numbers