# Service codes The USSD channel relies on one of three service codes: 1. **Dedicated service code**: A code typically owned by one account and used by only one user for their company or service. It only has one segment, for example, \*111#. You can add as many sub-codes (extensions) as you want. 2. **Semi-dedicated service code**: A code dedicated to one account but shared among other accounts. 3. **Shared service** **code**: A code that is shared and used by multiple companies or services. Each company is allocated a channel on Clickatell's dedicated sub-code but the dedicated parent code is shared. You can add as many sub-codes (extensions) as you want, for example, \*111\*01\*xxx#. {% hint style="info" %} The USSD bearer is accessed by calling a number that starts with the asterisk "\*" or hash/pound sign "#", followed by a combination of numerals, asterisks, and finally the hash/pound sign. {% endhint %} --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://guides.clickatell.com/ussd-user-guide/getting-started/service-codes.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.