When I am updating my GO 5000 I get offered a deal on speed camera updates (today it was 3mth for 99p) but when I got to try and buy them I get an error: "Vouchers can only be used 1 time when purchasing a subscription. You have purchased a subscription in the past using a voucher. We have removed the voucher from your order. You can now proceed with your order by clicking the place order button.".
Why am I being offered the deal if I cannot use it, this has happened more than once over the last few months?