Tidio offers a forever free version - Tidio Chat Basic.
Each Tidio account starts with a free trial and once the trial is over, you will have to decide if you wish to continue with a paid subscription or downgrade your account to a Basic version.
To downgrade your account to Basic, click the "Select your plan" button and select "Downgrade to Basic" option.
You will see a message asking whether you still want to downgrade your account. Choose the “Yes, downgrade my account” option. Your account will now be set to Basic.