So, your trusty old PBX has been sitting in your IT closet for years, a verifiable workhorse. Yes, it has served faithfully for years. But all good things must come to an end, and an old on-premise PBX might be costing you money, making your customer experience sub-optimal, or even make you vulnerable to disasters. So, do you need to say goodbye to your own on-premise PBX? Here are a few signs. If you make a lot of long-distance calls, it’s important to understand that VoIP calls and PBX calls are billed differently.