When you say extension 7020, do you mean 7020 is the extension number that is dialed to reach the user?
If so, then 7020 is what is called the "extensionNumber" in our API which can be used for dialing purposes. However, the number in the REST API path is the "extensionId" which is a different number. To retrieve a list of extensions call the extension (account/{accountId}/extension) endpoint and you will get a list of extensions back with both and "id" (aka "extensionId") property and an "extensionNumber". The "id" property is the one that is used in the REST API path.
