thanks for your response.

Sorry I'm quite new to Freeswitch/linux, what is a PCAP?

I was leaning towards it being the carrier as omitting dropt_dtmf results in the full tone being transmitted. My issue is that I cannot see how to test is this in fact the case.

Using the dialplan shown in my original emails and setting the log level to 7, when making the call I can see the DTMF tones coming in but am unsure if this is the inband being reported or the out-of band.

thanks

Matt