Unless you are in my contacts you won't get through
I think this along with other modern technologies on phones (the main obstical or tool in the process) could be contributing to a decline.
Business number identification on the caller screen, sometimes marked as spam by other users or reviewers who may not have given the caller a fair assesement, could lead to your companies attempts being wasted.
The call wont even ring on the phone.
These settings are on by default on some handsets, hiya I think is one I saw on a Samsung for example.
People are quick to mark things as spam and leave negative reviews.
My advice to overcome this, as an outsider, would be to check your number isn't 'spam listed' or negatively reviewed on the web. Perhaps have the number you call from listed on the Web so its easily searchable and linked to some information about your company.
Perhaps send a text message with a website link prior to calling so the recipient can search you up.
Not many like unwanted door callers, in todays word a person's telephone number is their door to the outside world.
Also I find that many now a days prefer to find their own deals, info etc and act upon rather than accept anyone's help or offerings as they feel more comfortable knowing they have made an informed decision and perhaps don't want to have to make a decision on the spot.
Lasly I'm not sure of your audience but I have noticed that in my sector, very very little want to talk on the phone, they prefer to message back and forth for days - this could be for various reasons to do with modern life, time or location constraints eg imagine being on a bus or around kids, anxiety issues so many factors that I feel will be highly impacting telesales currently or in the future.