Delete many network configurations at once
You can use the Terminal to delete them out:

Usage: networksetup -removenetworkservice &lt;networkservice&gt;
    Remove the service named &lt;networkservice&gt;. Will fail if this is the only service on the hardware port that &lt;networkservice&gt; 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.