Does anyone say “can I swap seats with you/ can we swap seats?” instead of “can I switch seats with you?” in contexts of trains or planes?

Grammar: Either is fine. Reponse: No, I paid for this ticket to have the window seat near the front. I’m not going to switch/swap to your middle seat in the back

You can say both. If you mean public transport if you’re getting off next stop and they’re boarding/getting on and thus getting off later than you, feel free. If you’re doing it on a paid for specific seats in advance train (ie long distance), you better have a reason why lol

yes I would say this.

Yes, this is a very normal thing to say.

Yea switch and swap mean the exact same things

Yeah it means the same thing

Both of those would sound totally normal to me. I think I’d be more likely to use “switch” if we’re already sitting and “swap” when talking about assigned seats we haven’t reached yet. That might just be me though.

yes, they mean the same thing

Are you asking about swap vs. switch? They're synonyms in this context.

I do

In fact, I would say that in British English "swapping seats" sounds much more natural than switching.

This would be normal in British English - you won’t hear ‘switch seats’.

Yes, same meaning. I'd be more likely to say "swap", actually.

You can switch and swap the words switch and swap as a verb almost always.

Both are acceptable and used.

I would always say swap, never switch. But I'd understand switch as obviously fine. Australian.

Yes but I paid for these seats I will not get up. 

Absolutely can be used interchangeably. I rarely use the word switch in any context other than the mechanism used to turn something off or on (light switch, power switch etc..) swap is my go to word in the situation you describe.

Perfectly clear English. Not clear on the concept of “assigned seats.”

switch is quite american “can we switch? (seats being implied in the context of the situation)” whereas british and irish english would use swap from experience

Yes, they’re interchangeable

I tend to say 'switch places' or 'switch seats' if I want to swap with the other person. But, 'swap places' and 'swap seats' works too. I guess when I hear 'swap' I think of something I'll get to keep, but that's probably being very pedantic. Like if my daughter and I get presents and we decide to 'swap' them. 'Can we change seats' would mean can we find a different set of seats. Eta am Australian

Yeah, that sounds normal

Sure, “swap” can be used.

I don't know whether either is "technically correct," but everything you said sounds normal.