I struggled with this last night, then realized the docs are incorrect vs how the API works. There's an open issue for this (issue #95) as well.
Updating docs and example files to match the API.
Actually, if you have the latest version of the gem, @client.account.messages.create(...) should work. This uses the new Messages API and will eventually be the only way to send messages with the Gem in a later major version. Twilio is trying to move away from the /SMS/ prefix because it is unnecessary and the Messages API does not discriminate between SMS and MMS.
I'm going to close this for now in an effort to tidy up the PR list, but it would be awesome if you could point out if you indeed have an old version of the gem and also which docs gave you confusion so that Twilio can get the feedback! Thanks!
Looking at my Gemfile.lock, it is using 3.7.0 of twilio-ruby. I was developing off the README.md at https://github.com/twilio/twilio-ruby which didn't work for my code.
Gotchya, yea the new API was implemented in version 3.11, so if you update your Gemfile to use that version or greater, you should be good:
gem 'twilio-ruby', '~>3.11'
To my knowledge, upgrading should be smooth and backwards-compatible, so it is worth bumping the version and testing to see if everything in your app still works. The .sms. endpoint still works in this version.