Their mistake - my problem

On 2019/10/10 I underwent an operation at Unitas and all claims was paid by my Medical aid. I had an outstanding amount of R65.00 at Unitas which was sent to my email and paid forthwith. On 10/09/2020 (almost a year later) I received an email from Lancet for the amount of R361.80. I immediately called Lancet and queried this late statement. I have medical gap cover, so would have paid and claimed back this amount if received in time. The call center agent committed to escalate my query and return with a response. No response of course! My wife then received an SMS on her phone for the same amount. I once again called Lancet and requested a reason for the delay and why I am now liable for this money. I was informed that they used the contact details from the Unitas system and that they are not responsible if the information is incorrect. A couple of points here: I did receive and pay an invoice from Unitas (as stated above). I do not have access to or can check whether the system is updated if new info is provided. I have used Lancet in the interim (not through a hospital) and provided my contact details. I am now being harassed by and ITC company and after numerous mails and request to get a contact person that can actually explain how I am now liable for info that I did not provide (mails sent to Khayelihle Pelembe) still no response. SHAME on you Lancet! Your administrative inefficiencies are passed on to your UNWILLING clients and you do not even have the decency to respond to emails.