I would like to pay my bill but my Visa card has refused to work, currently I am in Juba South Sudan
My application has failed to update and even to download
There isn't an iTunes Store in South Sudan, so you must have put a different country on the account - using a country's store when not in that country isn't allowed. You can only use a card issued by a bank in the country that you have on the account, and it has to be registered to the same name and address as on the account.
And it's not a good idea to post your email address on a public forum, unless you like spam emails.