We just installed a GSM Gateway from Gempro: http://www.gempro.com.tw/ It is inexpensive, small and it even works. Sound quality is good. Setup is very similar to Portech products, for those who use it, but the approach is innovative. The gateways don't have a built-in phone but a bluetooth interface. They pair with an ordinary GSM phone using bluetooth and the use the phone to place and receive calls. On the 3CX side, we got it running with the same settings of the old-burned Portech gateway we were substituting.