2N BlueTower is the optimal solution for medium-sized companies with a high frequency of calls to mobile networks. This is a GSM / UMTS gateway, which can significantly reduce the cost of telephone calls. Its efficient router is able to find the cheapest connection route and will always use the most favorable direction (SIM-card).
Netropolitan Works builds secure VOIP in Thailand Asterisk systems and can do it in a way that makes sense for your business! http://www.NetropolitanWorks.com/VOIP-Thailand-lp.html