Communications hub for a Walk-a-thon?

I run the logistics for a large Walk-a-thon that maintains a communications hub during the event. For years, we set up 4 four phones which were given a hunt line (meaning, a call would come into the 1st phone and then bounce to the second if the first phone was busy.) The problem with this is that it’s a temporary location. Last year, we introduced a Skype call center that greatly upgraded the operation but we had difficulty with dropped calls and crashing computers. Any suggestions about other call center programs or any other communication options where volunteers can call in all along the route and receive instruction?