While YouMail is unable to block Spam text messages from being received, we are able to filter them so they do not clutter your Messages app. The YouMail app would need to be installed on your device for the option to be available. Once installed, please follow these steps to enable the setting:
Open your iPhone Settings and find the "Messages" tab.
Once the Messages tab is selected, scroll down to find the "Unknown & Spam" option. It will be under your "Message Filtering" setting.
From here, make sure that YouMail is enabled under your "SMS Filtering" setting.
Once YouMail is enabled there will be a new tab in your Messages app. Any spam or junk text messages will appear there.