Unable to answer phone calls


I set two extensions and I downloaded SIP applications on two iPhones. When I dial the other person’s extension, it rings, and when I click answer, it is not answering… I keep hearing the ringing tone even though I answered.

My freepbx is behind a router. I forwarded ports 5060, and 10,000 to 20,000. I also set Nat = yes in the extensions and in sip advanced settings. I also set qualify = no.

Please help…