What would be a good wireless "walkie talkie" device for use in a winery with a wine cave?

We constantly have problems during crush communicating with people in the wine caves while crushing wine up on an outside crushpad. we need a nextel type device so we can contact the team in the wine caves below as well as allowing them to reach the team up top. Currently, we have to take an elevator up or down to communicate.What would be a good wireless "walkie talkie" device for use in a winery with a wine cave?
You would probably need to go with nextel because they have a phone that supports that system.

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