Silver Plan: Billing - 50% Discount

I am a loyal customer, currently paying 39/month for Silver.

You are offering Silver at 19.50 per month.

How do I take advantage of this offer?

The discounted prices are valid only for up-sell subscriptions. In other words, as your current plan is Silver, you see the discounted price for Gold plans only. 

Also, I would like to point out that Black Friday campaign is applied to yearly and bi-yearly subscriptions, not monthly. When you upgrade your account to Gold yearly with discount, you will pay USD 594,00 in advance but the monthly rate will be USD 49,50.