Who I have the same questioned this topic

     I have a remote control device hooked to my MIFI device , but it has issues with DTMF tones when called from Iphone devices. If I call the MIFI from a standard POTS telephone the touch tones work correctly. I have tried several Iphones and have the same results. It appears that the Iphone touch tones are "too" short in duration. Is there a way to lengthen the DTMF tones on the Iphone?