=IF(OR($D$102="",$D$36=""),"",IF(AND($D$102>0,$D$36="Direct Debit "),"Direct Debit Acct" & $D$102,$D$36))
Maybe that?
BTW, using "Direct Debit" & " " & .... is unnecessary. Just add the space to the end of "Direct Debit ". That's why mine might look different than yours.