*** I am not a teacher ***
I think the author is using the present tense to give the passage a more informal, conversational feel. Some people, especially those less educated, might use the present tense like this in conversation when telling a story to make the events sound more exciting.
To make the passage grammatically correct, you would say "The next thing I knew, I was getting late charges and collection calls ...going into the thousands of dollars, he stole $200 from me?"
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