You can use Ubersuggest PRO absolutely free of charge during the 7-day trial period.
Your credit/debit card will only be charged once the initial free-trial period of seven days has been completed.
During the seven days of the free trial, however, you won’t be charged anything.
You may get a notice from your credit card saying you have been charged $0, though. This is quite common.
If you don’t want to be charged, you need to cancel the free trial before the seven days is up.