The Colombian prostitute behind the massive Secret Service scandal is finally admitting she had sex with one of the agents -- claiming he seriously short-changed her for her services, paying only $50 ... when she explicitly asked for $800.

24-year-old Dania Londono Suarez appeared on "Today" this morning with a translator -- claiming the agent was very direct about asking for sex when they met at a Cartagena bar last month.

Dania says she told him up front ... a night with her would cost $800 -- but the next morning, after they had had sex, the agent grew "very angry" when she asked for her money.

According to Dania, he threw her $50 and kicked her out -- and that's when police got involved.

The agent in question has reportedly resigned.

The Colombian prostitute behind the massive Secret Service scandal claims she had access to top secret government info during her tryst with an SS agent -- because he was passed out drunk.

24-year-old Dania Londono Suarez just appeared on wRadio in Colombia, claiming she even had access to the agent's wallet -- because he had fallen into a deep alcohol-induced slumber ... and left all his possessions completely unattended. Dania did not say if she actually rifled through his stuff.

Dania also didn't say if she actually had sex with the agent in question -- but admitted she did enough to warrant payment ... whatever that means.

And big surprise -- Dania said a lot more went down that fateful night in Cartagena, but she'll only divulge those secrets ... for a hefty price. She's already lawyered up with one of Colombia's best attorneys.

Good thing she wasn't a spy -- OR WAS SHE?!?!

Jimmy Fallon got one hell of an exclusive out of Barack Obama on his talk show last night ... he got the POTUS to finally open up about the "knuckleheads" he 86'd in the wake of the Secret Service hooker scandal.

Obama told Fallon ... "The Secret Service guys are incredible ... they protect me, they protect Michelle, they protect our girls, they protect our officials all around the world."

"99.9% of them, every day, they're putting their life on the line, they do a great job. So, a couple of knuckleheads shouldn't detract from what they do."

"What these guys were thinking? I don't know" ... Obama said ... adding, "That's why they're not there anymore."

Obama didn't just talk politics ... he also SANG politics ... in Fallon's, "Slow Jam the News" segment ... pretty awesome.

Here she is ... the 24-year-old Colombian prostitute who took down the Secret Service ... this according to the NY Daily News.

The paper claims the woman is a single mother named Dania ... who argued with a Secret Service agent about the price of sex during an alleged encounter in Cartagena last week.

Dania reportedly claims she demanded $800 for a night of boom boom ... but the agent only wanted to pay $30 ... and a massive argument ensued.

The agents are now under investigation ... and their lives and careers are in shambles ... buuuuuuut she is pretty hot.