HELP! Receiving lump payments from MYOB & not matching?

Bear with me, still fairly new to MYOB but I can't for the life of me understand how to wrap my head around this.

I run a service-based business, so sometimes sending multiple invoices a day to clients via MYOB. All good there- but when MYOB deposits the funds into my account 2-3 days later, I'm assuming is a lump sum payment of said invoices that were paid. 

The issue I'm finding is sometimes MYOB will automatically match it, but other times its unallocated. As it's a lump sum, I obviously need to link it to the invoices to match the amount? But I'm having a hard time trying to find and match these multiple transactions, I also haven't been getting customers to put in a reference number when paying so I have no idea what's what... as there's multiple invoices, with different amounts. All I can see is that it's been paid, and the invoice number but that doesn't match the description on the transaction either?

I hope this makes sense to somebody!!! Thankyou