Hi Christopher,
The only way to chat with someone for free on eHarmony is when eHarmony is doing a Free Communication Weekend.
They normally do these on or around special occasions or holidays such as Valentine’s Day, St Patrick’s Day, Thanksgiving and even Christmas. They can also do them on random weekends as well. There is no set schedule for when they do these.
If you are signed up on eHarmony, you will normally get a notification by email when they are about to have a Free Communication Weekend. Otherwise, you can always follow them on social media. They make announcements there too whenever a Free Communication Weekend is imminent.
These give you an opportunity to communicate with matches for free for up to 3 days or so.
Other than this, there is really no other way to communicate for free with a match through messaging on eHarmony. The only other thing you could try is pay for a membership and then cancel or close your account within 3 days.
eHarmony will not refund your money if you go beyond the first 3 days of premium membership. 3 days is not that much time to find a match, but if you have a killer dating profile, you may get lucky. Other than that, you are out of luck.
There are lots of free dating sites and apps out there. Perhaps try those?