Calling sendTextMessage after sending MMS causes message to be incorrectly sent as MMS

[rsml]

Expected result:
Message should be sent as SMS anytime you call sendTextMessage. I'm seeing in the console that the message is being sent as an MMS.

I think the cause is that I previously sent an MMS and CM is somewhere remembering that my allowedChannels is ["MMS"].

I'll submit a pull request shortly.