Some minor grammar fixes

Perusing the billing documentation to better understand the topic for my clients, and I thought I'd tweak a few things. Forgive my OCD. 😄

Author: WesleyDavid

articles/billing/billing-how-to-change-credit-card.md

@@ -20,7 +20,7 @@ ms.author: cwatson
 ---
 # Add, update, or remove a credit or debit card for Azure
 
-In the Account Center, you can add a new credit card, update an existing credit card, or delete a credit card that you don't use. You must be [Account Administrator](billing-subscription-transfer.md#whoisaa) to make these changes.
+In the Account Center, you can add a new credit card, update an existing credit card, or delete a credit card that you don't use. You must be an [Account Administrator](billing-subscription-transfer.md#whoisaa) to make these changes.
 
 **Want to switch to pay by invoice?** See [Pay for Azure subscriptions by invoice](billing-how-to-pay-by-invoice.md).
 
@@ -78,7 +78,7 @@ If you need to remove your credit or debit card before the 90-day retention peri
 
 ### Why do I keep getting "Your login session has expired. Please click here to log back in"?
 
-If you keep getting this error message even if already you logged out and back in, try again with a private browsing session.
+If you keep getting this error message even if you've already logged out and back in, try again with a private browsing session.
 
 ### How do I use a different card for each subscription I have?