You can set the sender ID of your choice by adding it in your account and once approved you can use it to send SMS. Alphanumeric Sender ID are allowed only if you submit relevant supporting documents(Trademark, brand, registration, company registration) and undertaking on your letterhead. Sender ID is a combination of numeric and alpha or only alpha characters (0-9, a-z, A-Z, _). It's dynamically setup by the user. Maximum length of alphanumeric SMS Sender ID is 11 characters. Due to regulatory issues, some countries are limited to 8 characters.