We would like to, first of all, thank you for using our services. With regards to call termination issues to Iowa and Minnesota as you have reported, we apologize for the inconvenience as this problem relates to call restrictions to these destinations. Unfortunately, the situation that led to the restrictions is beyond our control as enormous rates leave us with the unfortunate position that we are hereby advising of.

This restriction is imposed due to rate hikes of approximately 1841% to several NPA-NXXs in Iowa and Minnesota. The percentage is not exaggerated. This rate hike is due to the Independent Phone Companies that operate these NPA-NXXs teaming up with companies offering free calling services. This is causing a drastic increase in the volume of calls Local Exchange Carriers (LECs) terminate to these areas.

The Independent Phone Companies’ settlement rates billed to the LECs is very costly, much higher than standard Bill and Keep rates charged between two LECs. Several LECs in the US have filed complaints with the US regulators (FCC) to have this practice stopped because their costs are absolutely crippling. Here’s a link to one of the news articles if you’re interested that outlines the problem rather descriptively.
http://gigaom.com/2007/02/23/iowa-free-calling-schemes/

https://en.wikipedia.org/wiki/Area_code_641

As a result, an executive decision was made by the governing bodies of Distributel (parent company to ThinkTel) to limit/restrict traffic to NPA-NXXs for the rate centers below. This, unfortunately, means that at times you will not be able to complete calls to the destinations.

What you will experience when calling during the even hours, i.e. 00:00 to 00:59, 02:00 to 02:59, and 22:00 to 22:99, is that calls will be restricted to only allow a small number of calls to these NPA-NXXs through at a time. Additional calls will be terminated with a fast busy or treatment stating that “the number you have dialled cannot be reached from this line”.

During the odd hours, i.e. 01:00 to 01:59, 03:00 to 03:59, and 23:00 to 23:59, all calls to theses NPA-NXXs will be terminated with a fast busy treatment or treatment stating that “the number you have dialled cannot be reached from this line”.

Calls will not be suddenly terminated if the time changes from an even hour to an odd hour; the call will stay up until someone hangs up.

The affected NPA-NXXs are:

We apologize for any inconvenience that this issue presents to you or your customers. Unfortunately, there’s nothing that we’re able to do to change the reality of the situation.

Please contact your account representative if you have additional questions or concerns regarding this matter.