Looking for advice on Service Management solution

I work for a local WISP and my company is looking for a solid service management solution that includes Help Desk/Ticketing, Scheduling, Equipment Management and Customer Management/Billing. We have been using a custom database app and Tucow's Platypus for billing. We'd been exploring the Platypus Wombat extension for Help Desk, but it's just not meeting our needs. Any input or advice from other WISPs would be greatly appreciated.