I have a question about whether "I didn't have no plans" is correct or not, since I think that it's a double negation and therefore not correct, so it should be "I didn't have any plans". However, I'm not sure if it's really wrong.
"I didn't have no plans" is correct standard English, meaning "I did have some plans", (with a nuance that "I only had a few plans") This is rare in actual use, and the word "no" would be stressed.
It is also common in non-standard English as a synonym of "I didn't have any plans".
Why didn't you have the plans?
I didn't have no plans, but I only took a couple of plans that I thought were most useful. With hindsight, I should have taken more.
What are your plans?
Look buddy, I don't have no plans! I'm just gonna ride the rails f'ra bit.