Cannot make payment through global payments

I am trying to make a payment into my channel islands account, but I keep getting error message 180 stating that my SWIFT code is not valid. I have tried to make payment by adding my channel islands account as a beneficiary and then making payment, as well as trying to make a once-off payment, but the error is the same. I have spoken to 2 people in your Forex call centre, which is a nightmare to get hold of due to the hold time. The first person told me that the GG in my Swift code should be JJ, but the system prepopulates the Swift code, so how do I change the GG to a JJ? The second person told me that the GG is correct, but I must make payment as a once off payment and not by adding my account as a beneficiary. Please can somebody help me sort this out. I am not phoning your Forex call centre again as the hold time is far too long.