Since you have a trial account it will end on it's own at the end of the time period. You don't need to take any action to close it. If you make your account a paid account in the future you will need to give us a call as @Clique_Marketing mentioned.
We do not have an option to delete trial accounts as they expire in time automatically if no credit card is added to the account. You can leave your account to expire, which will happen within 55 days from today.
@Clique_Marketing is right about a paid account but since your account is still in trial you can just let it end on it's own. It looks like you have 59 days left. You haven't entered any credit card information so when the 59 days are up the account will end for you.
I am sorry to hear you need to close the account. Since your account is still in trial you can just let it end on it's own. I will go ahead and turn your communication notifications to do not call for you moving forward.