Upgrading from Bronze to Silver - bill the difference?

I need to upgrade from Bronze to Silver but I'm only a week into this month's billing.  Will I be billed $39 or the $20 difference between the Bronze and Silver plans?

I've refunded your 19$ that you paid on Dec/4/2015.

Now, you can upgrade your plan to Silver now.

Please, check the guide below for more information:

http://www.jotform.com/pricing

If you require any further information, feel free to contact us. We will be happy to assist you.

I was wondering why it was refunded when I had not yet upgraded. I was waiting for a response as to whether we wanted a month or a year. I quickly upgraded for the month so that the account wasn’t cancelled. I may still upgrade to the year next month.
Thanks – Ginny
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On behalf of my colleague, you are welcome! If you need anything else please open a new thread, we will be glad to assist you.