WTF AxVoice? Never heard of them. I looked at their website. Their forum posts are all older than 2012, with no information about setting up third-party ATAs, and a lot of broken links. I couldn't even get to their instructions about setting up their own ATA, which is included for the price of service. IF you really want to use this company's service, good luck, but why not just use the free ATA that they give you?
And, there is no OBi 201. There is a single phone port OBi 200, and a dual phone port 202. If, for some unfathomable reason, you wanted to use an OBi instead of their ATA, then buy a 200 from Amazon.