VOIP/PBX Hosted Solution for SMB

[mdfi13]

Currently we have an old Nortel PBX solutions that we would like to replace with a Hosted service provider via VOIP.

Here is our criteria:
- We need to port our DID numbers to the new service.
- Softphone or handset option.
- No Hardware required.
- Easily manage the setup and administration of users, lines, and features centrally (via the web).
- Must not be a fly by night company. A company with a good reputation.
- Support for 500+ users.

Can you please give me your recommendations.

Thanks