I worked in Telco line once (that was long long time ago, in the galaxy far, far away.... ops, sorry, back to topic),
the prefix is not assign with single digit in Mobile phone company. To make it simple.
Example, for Maxis, assign the following range of number
012 - 294 xxxx (Klang Valley)
012 - 295 xxxx (Perak)
The (prefix) number (294 and 295) might be next to each other, but it actually indicate different location where this number Maxis assigned to.
Of course Maxis won't make it so complicated, usually it will be
(Klang Valley)
012 - 290 0000 to 012 - 294 9999
012 - 390 0000 to 012 - 395 9999
(Perak)
012 - 295 0000 to 012 - 299 9999
NOT 012 - 9xx xxxx (Perak) (This indicate anything start with 9 after 012 is assigned to Perak)
Same thing with Telekom Malaysia, there are definitely more than 1 prefix (after 03) assign to Cheras, but the prefix may or may not sit next to each other.
and of course, maybe you guys just want to simplified the situation hence you just put 1 digit after the telco prefix (012) as an example here.