How to let customers pay by telephone and fax?

Dear friends
I have received some request from customers rescently.
They don't feel comfortable to pay by credit card online although our site is covered by https. They would like to pay by telephone or fax.
But I don't know how to do that. I don't know how to let customers pay by telephone & fax and I don't know how to receive money by doing that way.
Can anybody help explain this kind of payment method?

You will need an EFTPOS terminal for card processing (Electronic Funds Transfer at Point Of Sale) and you will need to talk to your card clearing bank about this. It is not a zencart issue.

Some providers have systems where your mobile phone (cellphone) can act as a EFTPOS terminal, so the transaction can be completed on your telephone handset.

Again, not a zencart issue. Google "Accepting Credit Card Payements on a Mobile Phone / Cellphone" .

HERE is an example