Echo Connect - Invalid phone number

[swalwick]

I have an echo connect and would like to use voice controls to open and close my driveway gate.  To open and close my gate I use my landline phone and dial ##81# (to open) and ##83# (to close).  I have added "Open Gate" and "Close Gate" to my contacts with phone numbers ##81# and ##83#, but when I ask Alexa to "Call Open Gate"...Alexa Connect will not dial ##81# and Alexa simply replies "Sorry...that is not a valid phone number".  Any ideas how to get around this?

Thanks.  Sean W.