You can use the Terminal to delete them out:
Usage: networksetup -removenetworkservice <networkservice>
Remove the service named <networkservice>. Will fail if this is the only service on the hardware port that <networkservice> is on.
To get it to list then remove all the ones with MT65XX you'd need to do something like:
$ services=("${(@f)$(networksetup -listallnetworkservices | grep MT65XX | sed s/\*//)}")
$ for service in $services[@]; do networksetup -removenetworkservice $service; done
That this does is builds a list of services by running:
networksetup -listallnetworkservices | grep MT65XX | sed s/\*//
The @f splits the list on newlines, ignoring spaces. The grep finds just the MT65XX lines, and the sed removes any *, which denote disabled services in the output.
Then, for each of those, it runs the networksetup -removenetworkservice step.