Try this, I found it from another forum and saved it because I'm also thinking of getting an ATA to use with my Onesuite SuiteAdvantage.
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Gateway:
userid@voip.onesuite.com
GW1 AuthID: onesuite username
GW1 Password: onesuite SA password
GW! Nat Mapping Enable: YES
Proxy: voip.onesuite.com
UserID: myuserid
Password: onesuite_broadband_password
Display Name: MyName
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