I thnik Steve CM and Crystal have got it spot on.
When i take on a residential customer i let them know the frequency and that i will only let them know prior to each visit if there is an issue with access (i.e padlocked gate) however if a customer has a padlocked gate i do ask them initially if they mind me climbing over it..
Some agree to this and thats fine, some don't and so i tell them the only way that i inform customers with access issues is via sms text message.
I used to text from my work mobile but soon learned that that some customers found it easy to send a reply text with excuses 'leave it this time' etc.
So what i have now works great and looks very professional. I use a company called Fast SMS and my text messages are sent from web software on my laptop, when the customer gets the text it does not show my number but shows my business name which you cannot send a reply to. I have also barred incoming texts to my work mobile as i say to customers the text service is there for info purposes only, and all correspondance is by phone or email only.
Its great also as you can schedule when you want the text to be sent ( time and date) so if you have a weekend away for example you could sort out your access texts on thursday to be sent on sunday tea time ready for work on Monday.
If they really have a problem they all have my email and mobile number, and i tell them to call and leave a voicemail and occasioanaly some do. IMO customers find it easy to fob you off via a text message but it is much harder for them to do it verbally.
You need control of your customers and not the other way round otherwise it is so hard to keep your revenue consistant. Phoning or contacting every customer the night before is time consuming and gives the customer the opportunity to make a lame excuse losing you the revenue, even though the customer agreed to your schedule.