NO banking and statements want to be provided

I recently received a call from MBD attorneys on an old outstanding account that I have. The consultant/ collection agent that I spoke to asked for a payment to made, we came to an agreement for a suitable amount that can be paid each month.

I asked for banking details to please be sent through to me, so that I can make payment, I did mentioned that I will not provide banking details for a debit order, as I don't want incorrect amounts to be run on my bank account.

As I asked for the banking details, I was told that these cannot be provided to me via a letter or email, but they can be provided to me over the phone, with the amount of ********** activities, I cannot just pay cash over to an account number provided to me over the phone, I need some proof of who I am paying, I clearly do not understand how attorneys can work this way.

This coming from an attorney firm, how is it possible that banking details and a statement cannot be provided? so how do I know who I am paying.

When I asked again for banking details to be sent on a letter head or from an email address, she sent it could not be sent, she will give them to me over the phone.

I don't trust this at all.