How to Delete a Message on a Windows Phone
If you send and receive lots of text messages, those messages can accumulate and take up quite a significant amount of space on your device. Not only does your device store all the text messages that you send and receive, but it also hangs onto photo and video attachments as well. This guide will teach you how to free up space by removing messages.
Be careful when deleting text messages from your device, as there is no practical way to retrieve them once they have been removed.