Seems like you've narrowed this issue down to your specific device and DTMF tones, only during WiFi Calling.
As always, make sure you've got the latest update for your device. Sounds like you've tried the normal stuff, restarting, etc.
This document addresses a semi-related problem with DTMF tones. Some information in there may be useful to you, but the document doesn't exactly describe the problem you're having.
Another thing that may help, clear the cache in the WiFi calling app. To do that, just go to settings>applications>manage applications then find WiFi calling, and tap "clear cache".
As a last resort, you can try a master reset. Of course this erases everything stored on the phone, so please make sure you've backed up important stuff before this so you don't lose anything that you can't get back during the reset. This may help prepare.
It sounds very unlikely this issue is hardware related, so one way or the other, you ought to be able to reset the WiFi calling app to clear this up.
Good luck, hope this helps!
Thanks for the info.
I am 100% up to date and use MyBackupPro to perform device backups then move those to my computer.
Re: clear wifi calling app cache:
I cannot clear wifi calling cache as it shows there is none used and all options are greyed out. I also diasbled wifi and checked again.I disabled wifi calling and checked again. I tried to insert a 12KB image but get the following error:
You don't have permission to do the requested action. You might need to log in to the system before you can continue.
It appears you're not allowed to view what you requested. You might contact your administrator if you think this is a mistake. "
The support doc you linked might have actually done the trick. Turning off "audible touch tones" at first test seems to have worked. I still hear the tones I press but I do not hear any echo or doubling.Sweet!
This is great because I have no desire whatsoever to wipe my device and if I did I would be looking hard at rooting (wifi/usb tethering would be nice)
Thanks very much. If I find the issue resurfaces I will post back here.
You're very welcome.
Oh excellent, I use MyBackupPro and have since the G1 days, IMO best backup app on the market.
Glad to hear that, hope its cleared up for good. I can appreciate your hesitation to wipe, but at least your backup app will make it relatively easy to restore things after.
Please let us know how it goes.
Hope this information helps others, in case anyone else comes across this issue in the future.