Sounds like your problem isn't with VOIP, it's with softphone VOIP clients and/or OTT carrier. The company phones are probably VOIP (do they just have ethernet

Sounds like your problem isn't with VOIP, it's with softphone VOIP clients and/or OTT carrier. The company phones are probably VOIP (do they just have ethernet connections?), but connected up to a telco which handles traffic nicely. Most telcos are sending a huge amount of traffic round over IP. The difference is that they are controlling the bandwidth so stuff just-works, whereas when you use a purely OTT service, you're probably stuck with your packets getting the same treatment as any old web request. Most of the calls you think you can detect as POTS probably have VOIP legs in them somewhere if they're long distance. Which of the services are the most expensive? My guess is the company phone. Are you paying for any of the others?