Query Not Delivering Unique Records

I am trying to set up a query to select PaymentDate, CustSurname, CustForename, AgentName showing only the last record for each customer if the last payment is over 7 days and also include customers with no payment.

the table structure is:

tblLoans
LoanID (PK)
CustID (FK)
AgentID(FK)

tblPayments
PaymentID (PK)
PaymentDate
LoanID (FK)

tblAgents
AgentID (PK)
AgentName

tblCustomers
CustID (PK)
CustSurname
Custforename


I have tried the code as below: but it now gives me every payment for the defaulters as opposed to just the last defaulted payment. Can you shed any light on what I have done wrong.


select b.PaymentDate, a.CustSurname, a.Custforename, c.AgentName, d.LoanID
from tblCustomers a, tblPayments b, tblAgents c, tblLoans d
where d.LoanID = b.LoanID and d.CustID = a.CustID and d.AgentID = c.AgentID
and (DATE()-(SELECT max(PaymentDate) from tblPayments f where f.LoanID=d.LoanID ))>7
UNION select '' as PaymentDate, a.CustSurname, a.Custforename, c.AgentName, d.LoanID
from
tblCustomers a, tblLoans d, tblAgents c
where a.CustID = d.LoanID
and c.AgentID = d.AgentID
and (select count(*) from tblPayments where tblPayments.LoanID = d.LoanID) = 0;