The wikala will require proof. What is sufficient proof?

I've had this issue before. I was told by sheikhs I need proof and even when I gave them proof of text messages of the person in question explicitly saying what they do, they told me it wasn't sufficient and I need witness's but that's a bit problematic in regards to marriage.

Accepted proof:

1- Have him write it on a piece of paper, sign it, and have 2 just witnesses sign the paper so it cannot be denied later.

2- Have him voice record himself saying he has given you such a wikala in a binding contract.