Older native English speakers usually just go with "I said", at all levels of formality. You might hear "I says" in the past tense too. The increased separatio

Older native English speakers usually just go with "I said", at all levels of formality. You might hear "I says" in the past tense too. The increased separation of a "natural and spontaneous" register of English seems to have been mostly a function of 1970s-1990s youth culture - you can hear this in "candid microphone" radio shows before this period [1], where there's surprisingly little difference (to a young-ish native speaker like me) between the recorded colloquial usage and the formal standard English of speeches/literature/film. Lots mid-century film sounds stilted to us, but people actually spoke like that. [1] A big chunk of recordings are at https://www.youtube.com/watch?v=znyNNn5esXg https://www.youtube.com/watch?v=znyNNn5esXg