Even if somehow he managed to prove that he just bumped into a woman in the street and started dating her, and her profession happened to be sex work-
It is still reasonable for someone to conclude that he used her services, based on his previous confessions.
Let's imagine if the question is 'did tamalam buy groceries at Walmart?'
If you can show me saying I went to Walmart, had previously done so many times, spent X amount of time there, took money there, and left with groceries: It is reasonable to conclude I bought groceries there.
I could prove later (maybe via cctv) that I went inside and was handed groceries as a gift, or I was only retrieving groceries for someone else.
My proof does not make the original statement a defamatory lie. Because it was a reasonable conclusion made in good faith with the evidence available at the time. False, technically. But not defamatory. There has to be malice.