Being threatened to get blacklisted even without invoices or payments made

I’ve had my jet account for a couple of months and have only received 1 text as a reminder to make payment. Every month I get either an unsolicited email or text to “remind” me to make payment or get blacklisted. They never send statements to show what I owe and when payments are due or how much is due . I went into store and asked for an invoice , was told they don’t give them out nor send them, then called head office , a statement was sent but that was the last one i received . However I keep getting emails to threaten me of getting blacklisted!Is this how you treat all your customers, had I known I wouldn’t have bothered to get an account with you.