What is the permission necessary to drop a service in service-broker? When I want to drop a service which is already created, this error happens:

Msg 15151, Level 16, State 1, Line 316
Cannot drop the service '//Audit/Contract', because it does not exist or you do not have permission.


My sql query to perform drop operation is:

IF EXISTS(SELECT * FROM sys.service_contracts  WHERE NAME = '//Audit/Contract')
    DROP SERVICE [//Audit/Contract]


So, the main question is: What is the permissions necessary to drop a service in service-broker?
After I post this question, I just found my answer with some tricky way. I went to the left object explorer and delete the contract with it. but instead of submitting the form I click on the script button which produces the scripts. It was my mistake to drop a contract with drop service command. so the correct query to drop a contract is:

IF EXISTS(SELECT * FROM sys.service_contracts  WHERE NAME = '//Audit/Contract')
    DROP CONTRACT [//Audit/Contract]


I post this answer because maybe somebody encounter with this error and my guide can be useful to him/her.