CORE CONCEPT: A decision made by a buyer to buy something always has been and always will be 'impulse buying'.  When someone decides they want to hire someone to clean their home they want to fulfill that decision NOW.  If you do not answer your phone they will call the next person in the yellow pages, on google or whatever.  If they are calling off of a flyer and you do not answer your phone they will go to google and find another company that does answer their phone.  You have just motivated them to do something and, really, you have advertised for the competitor that sells them.  If your  phone is not going to be answered do not spend money advertising. Voice mail works for your current clients but it does not work for new clients.  Buying is, and always will be, impulsive.  Why do you think car dealers do not let you off their lots without selling you something?  

RESOLUTION:  If you cannot answer your phone because you are dealing with problems in the office, cleaning homes (and you should NEVER answer a phone in front of a client) or changing a tire on a company car---then hire someone who can answer it for you.  This is another 'no brainer'.  If someone is not answering your phone you cannot grow.  If you cannot grow you will never get big enough to hire enough cleaners so you can stop cleaning and answer your phones.  You have yourself in a catch 22 that you will never get out of.  The solution is to hire it done until you can do it yourself.