Try our calling service; DUAL Talk. There is information on setting up a Cisco ATA 186 for DUAL Talk at dualtalk.com/ata186.htx.
In summary, make the following settings:
UID0 = [anything, but not 0]
UID1 = [anything, but not 0]
Gateway = 217.155.148.229
UseSIP = 0
AudioMode = 0x00140014
ConnectMode = 0x00060003
LBRCodec = 0
RxCodec = 0
TxCodec = 0
NumTxFrames = 1
Then, place a call to 123 to reach a recorded announcement. If you hear it, then you are setup correctly.
You then need to open a DUAL Talk Account to make real calls. We have many satisified customer using the service.
Please let us know if you need any help.
Kind regards,
DUAL Talk.