In order to disconnect from Authy and then move forward using SMS only, please follow these steps:
1) Have an Admin go to your User profile and disable 2FA (Admin -> Users) -> Set it to Password Only.
2) Follow the steps at the following link to delete the 2FA Account tokens from Authy: https://support.authy.com/hc/en-us/articles/115001836787-Delete-Hide-or-Decrypt-Two-Factor-Authentication-2FA-Account-Tokens-in-the-Authy-App
You'll see there are several sections and you can click on the link depending on your device:
Once you have done that, it will take up to 48 hours for it to be removed from Authy. It may take less time, but you may want to wait that timeframe before re-enabling in Recurly to ensure you don't experience any issues with using SMS to log in.