I, for example, have switched my home phone over to Verizon's VoIP service, which they have branded VoiceWing (snicker all you want). Cost: $29.95 per month. Vonage and other VoIP providers can be used for less, though I've found that $20 per month seems to be about the bargain basement for all you cheap-o's out there. Now, can you run your enterprise telephony needs on Vonage? Definitely not. But there are solutions out there to help enterprises drastically reduce their wireline telecom bills.
Now compare that small expenditure to my wireless bill, and it's night and day. I pay Verizon Wireless over $90 for a reasonable voice plan and a low-tier data plan. That's three times the cost, and it's not really all that much. I know power users who spend well over $150 a month for ridiculous buckets of minutes and basically have their wireless phones glued to their heads constantly (you know who I'm talking about, Ed).
At my last full-time job, I had a good old trusty PBX sitting on my desk and a work-provisioned BlackBerry. Honestly, I never touched my PBX. All it did was gather dust. My mom probably called me on that phone more than anyone else. My employer was, however, shelling out about $100 a month on my voice and data plan for the BlackBerry. There's no way my PBX bill, even lumped in with the overall organization, amounted to that much each month.
According to Insight, the total telecom bill for the US in 2006 was a whopping $132 billion, with fully one-third of that going to wireless communications. If you think the wireless companies aren't dancing for joy, don't kid yourself. The price wars of the last few years for wireline services resulted in better fees for enterprises, but the war is over, and prices aren't going anywhere for a while. Same goes for wireless.
The point of all this is, with the number of mobile employees requiring voice and data plans on the rise, enterprises can expect their cellular bills to rise as well. The key for cost-conscious enterprises is to negotiate with your local, long-distance and wireless providers and get the best batch of plans available. Don't be afraid to look at new technology, like VoIP other IP-based systems. Countless engineers worked hard on them to save you money. The least you could do is pay attention for a few moments.