Pulled over for speeding when I wasn't?

So about 2 weeks ago, I was cruising through Columbus, MS from a trip at 70mph (highway speed limit is 70mph). I saw a cop ahead of me and slowed down just a bit, and kept going. He pulled out and pulled right behind me. Literally I was so confused because I wasn't even speeding. When I pulled over, he hopped out the car and said he clocked me 84mph. I tried to talk with him and tell him I was not speeding, but he has a really nasty attitude and wouldn't even let me finish talking. He just issued me a ticket right away and sped off.

My court date is coming up soon and I'm not sure what to do. I have Life360 on my phone and it's kinda the only thing I can use to prove that I wasn't speeding. It says the highest speed I drove that trip was 74mph. I asked for advice from my family, but everyone keeps telling me that they won't taking my Life360 as evidence, and will believe the cop over me. I really don't have the money to pay ticket for something I DIDN'T DO😭

What can I do???