If you have a discount coupon you can upgrade to an Enterprise account.
To activate your discount coupon, please navigate to your "user id" on the top right corner, select "My organizations" and select "Billing". Click on "change" on plan section to upgrade to Basic or Enterprise. After entering your credit card and choosing the plan, you can enter your discount coupon (which is "XXXX", given by callstats.io).
Please make sure the following while entering the discount coupon :
+ You have entered the credit card details correctly.
+ You have entered the CVC number
+ You have entered the discount coupon code given to you.
Failing to enter any of the following details would result in getting your credit card charged.
Please remember to cancel the subscription on time as your credit card will be charged after the trial period offered by the discount coupon.