Getting Paid

[loveofducks]

I had an item listed for buy it now or best offer.  I had an offer for 60.00.  I accepted but did not receive payment.  Now the buyer said he stated he would pay on the 29th of this month.  I didn't see that in the best offer information.  I thought if best offer was excepted you needed to pay just like buy it now. 

What is the correct protocol?

Thank you,

Ellyn