If you're paying for a subscription, the company might sell your data. If you're using a commercial service for free, they are certainly selling your data.
Having said that, you're right to be suspicious of commercial services, even that you pay for. Someone can found a startup with a strong commitment to customer privacy and the best of intentions, but a few acquisitions or near bankruptcies later, those commitments will go out the window.
Relevant to this case, since they have a free version and premium one, they would probably just sell data from both sets of customers. It would be leaving money on the table otherwise, right?
The small chance that they might go out of their way to not sell premium users data doesn't seem worth much.