Closing an account is as much as easy to create a new one account on Cash app. But make sure, at the time of closing account, you have to verify your identity via providing all the details. As most of time, they ask to enter full username, date of birth, last four digits of SSN. So, put all to complete the verification process. For further, use Cash App Customer Service phone number.
https://www.contact-customer-service.net/customer-service/Cash-app
https://www.contact-customer-service.net/customer-service/Cash-app