I`ve already paid the invoice for my domain name...

Are you sure this is for the same domain name? Many clients have multiple domain names that look very similar...

For example...

MyCompanyName.com

and say...

MyCompanyName.co.uk

or...

My-Company-Name.com

If you`ve been invoiced and paid for one domain name, and are receiving another invoice, it might be for another variation of your domain name. Please double check. It`s extremely unlikely our system would invoice you twice for the same domain name and we promise we`re not crafty like that! :)