Netcare's accounts department lets the company down

I recently had to take my wife to Netcare Umhlanga's emergency department. Then, on Friday evening and again on Saturday evening they sent me sms messages saying I need to log on to their website because my profile has new bill info. Apparently I owe them money. But they have not sent me an invoice. The have my e-mail address but would rather harass me after hours on my phone a week after the first traumatic experience. There is no invoice available when I follow the link either, just a statement that lists an "accounting document". I have just tried to phone them to ask for an invoice and was on hold for 11 minutes before I gave up. You need to issue me an invoice if you want me to pay you, Netcare.