Need 16 digit DTMF IAX client for Iphone

Zoipper and Linphone only supports a 12 digit DTMF pad.

I need a 16 digit DTMF pad to send the 'A' 'B' 'C' 'D'digits

Does anybody know of any?

Thanks
73 Neil Sablatzky K8IT
Allstar Node 41838 KITLINK
Allstar Node 42087 KITLINK HUB
IRLP Node exp0068
Echolink K8IT-L
WIRES-X K8IT 11479 Room 21479