Sounds like an unpleasant set of encounters!

I'm a little confused by what you've said, also - these practices are not limited to debt; there are many neocolonial practices.

Most of the stuff I can think of to read is not succinct or digestible and I don't have anybody nearby to ask for better reading at the moment. The main thing that comes to mind as pretty short is probably the chapter "The Mechanisms of Neocolonialism" from Nkrumah's Neo-Colonialism: The Last Stage of Imperialism, perhaps ideally read together with the introduction.

There's also Rodney's How Europe Underdeveloped Africa, perhaps just the section "What Is Underdevelopment?" from the chapter “Some Questions on Development”. It's a book with some outdated notions while really being good at what it does.

It starts off with a nice Guevara quote (who speaks quite a bit on these topics I think but I don't know much about it):

In contrast with the surging growth of the countries in the socialist camp and the development taking place, albeit much more slowly, in the majority of the capitalist countries, is the unquestionable fact that a large proportion of the so-called underdeveloped countries are in total stagnation, and that in some of them the rate of economic growth is lower than that of population increase. These characteristics are not fortuitous; they correspond strictly to the nature of the capitalist system in full expansion, which transfers to the dependent countries the most abusive and barefaced forms of exploitation. It must be clearly understood that the only way to solve the questions now besetting mankind is to eliminate completely the exploitation of dependent countries by developed capitalist countries, with all the consequences that this implies.

(actually, that whole speech might be a good thing to read on the topic.)

and later, introducing the histories of changing exploitation, Rodney talks about how troublesome it got at one stage for the Roman empire to keep slaves:

The landowners, seeing their estates going to ruin, decided that it would be best to grant the legal freedom for which slaves were clamoring, and to keep exploiting the labor of these free serfs by insuring that they had no lands to plow other than those of the landlords. Thereby, a new set of social relations-that of landlord and serf-replaced the old relations of slavemaster and slave.

You can see the logic here - neocolonialism thinks of this in terms of whole other countries or continents.

Finally I'm reminded of a documentary I recently watched that was posted here called Congo, my precious, that does a pretty good job tying occurrences in Congo to continued exploitation by other countries, and might help you better to talk about it with them.

Sorry this wasn't a simple recommendation of a short sweet piece on the matter. I imagine that some exists but sadly I don't know it.