You must find all access points and close them off some how or it will
be very difficult to keep them out.
There are inexpensive ways to try and do that.
You can buy a door sweep that you attach by a couple of screws and it fills in
the opening at the bottom of your door. For garage doors you can buy black pipe
insulation and screw it to the bottom of the garage door so when it is closed it
will make a tight seal. These methods are cheap and easy.
Until you do something to block all the entry points they will keep coming in.
Also if you don't want to harm them then this is still your best bet.