Upgrade to Silver plan

Hi, I'm currently subscribed to your Bronze plan and I have paid for 1 year. I would like to upgrade that to your silver plan, but obviously I do not wish to pay the full price since I already paid for the bronze plan. Is there a way for me to just pay the difference?

Thank you in advance. 

It seems that you have already tried upgrading your account to Silver subscription. When upgrading the account to a higher plan, you'll be charged on pro-rata basis. As I check your account, a payment follow-up in process and our system would try to charge your card on Sep 25, 2015 for $276.32 USD. It looks like the payment was declined on your card ending 0511. If you need to change the credit card information or manage your subscription, please follow the link below :

https://sites.fastspring.com/interlogy/order/s/INT150606-3700-10396S

Hope this information helps!