Can I upgrade my plan later?

Yes. Upgrading is easy. Simply login to your admin dashboard with your username and password. Then, in your "Add/Renew Subscription" section, you will find a link to upgrade your account. 

Simply choose which plan you'd like to upgrade to at this point.

NOTE: The Forever Free Plan has  the following limitations:
1 operator, 40 chats, 15000 impressions and 30 offline emails(per month)