Phone numbers in Waterloo, Illinois
Waterloo has 4 phone prefixes in area code 618.
Biggest holders: T-Mobile (including Sprint), Harrisonville Tel. This is the local calling area (rate center) where those prefixes were first assigned.
- Mobile carrier 50%
- Phone company 50%
Every prefix in Waterloo
Search the first six digits of a number in this list. If it's here, the number started in Waterloo with the carrier shown. If it isn't, check the Illinois page or look the number up.
| Prefix | Carrier | Type | Assigned |
|---|---|---|---|
| 618-504 | T-Mobile (including Sprint) | Mobile carrier | 2010 |
| 618-938 | Harrisonville Tel | Phone company | – |
| 618-939 | Harrisonville Tel | Phone company | – |
| 618-986 | T-Mobile (including Sprint) | Mobile carrier | 2023 |
Most prefixes are pooled: the 10,000 numbers in each are handed out in blocks of 1,000 to different carriers, and people can also take their numbers to another carrier. So the carrier shown is where the prefix started, not a guarantee about any one number. Source: NANPA central office code records, 2026-10-10.