When creating an SMS send you can create a custom 'From name' that will show within your contact's phone inbox, known as your 'Sender ID':
When switching off your replies to display your custom Sender ID you can only insert a maximum of 11 alphanumeric characters, and shouldn't contain spaces or any other special characters.
This is a limit that has been in place since the early 90's, due to screen sizes being much smaller and therefore unlikely to fit the whole company name on the screen when receiving an SMS!
If you need any further assistance with creating or launching your SMS campaign, please reach out to the Customer Success Team via the instant chat in portal.