Caller: I called this number to get answers in regards invoices that have been sent to us

Over 10 years ago we used Engin as a VOIP provider, but all of a sudden started receiving invoices from them recently again. When I rang the number to question why, the line got cut off. I rang back and got the same customer officer I've previously spoken with!! What are the odds of this to happen? However she said they will cancel the account as of today. When I asked for the refund for couple of invoices my secretary have already paid, I was put on very long hold. The customer officer eventually came back asking for the bank details to send the money to. I replied that I would prefer the cheque as a more acceptable option (I was not happy to give them my bank details) to which she replied that they can't do that. I then asked to give me the total amount they are going to refund, as my way to check if they really have my invoices as I believe scammers would not keep a record of them, she said she would not have those details in front of her??? Then I asked for an email to be sent to me with the information as how much will be refunded and the email came with the yesterday's time stamp but without the amount to be refunded. Yesterday's time stamps explains the foreign accent of the person I was dealing with. The whole conversation was very uncomfortable for the customer officer as she often did not know how to reply or did not want to reply to my questions. I do not know if they are the real Engin company trying to get money from their customers who don't check their invoices or someone else got hold of Engin customers details and using them to get payments to their account. My concern is that it was paid with my CC that I still need to check if they have taken even more money of my account because nothing made me believe this was not some shifty work.

Pretend Phone/IT company fishing for information and stating that they have provided IT services and demanding that we pay. had some basic info of our company but did not have our licence number or correct phone number.
They have a Legitimate looking web site as well however intersting enough is that they do not provide any addresses or an ABN number.