blocked phrase still getting through???

I'm getting annoyed with all these junk invoice emails seems to be the same daily routine!! e.g.:-

subject line =

Invoice (13\03\2015) for payment to BANKERS INVESTMENT TRUST

Invoice (13\03\2015) for payment to STERLING ENERGY

Invoice (13\03\2015) for payment to BARONSMEAD VCT 3

....etc.

blank email with word documents attached!

so i block in the subject line

"Invoice (13\03\2015) for payment to"  regular expresion

"Invoice (13\03\2015) for payment to*"  as a string

"Invoice (13\03\2015) for payment to%"  as a string

"Invoice (13\03\2015)" as a string

"Invoice (13\03\2015)" regular expresion

yet they still get through to some users???