What if the other side's witness statement isn't true?

It is almost inevitable that you and the other side will have different accounts to give the tribunal of what happened (or did not), or you have different recollections as to what was said. This is normal: indeed if everyone agreed, it is unlikely you would be in a legal dispute with them!

It is also unlikely that, before hearing the evidence, the tribunal would agree with one party or another as to whether the witness has lied.

The way to challenge the matters you think are incorrect is to compare your statement with theirs, note any difference in the accounts and find contemporaneous evidence that supports your account or undermines theirs.

You will be expected to challenge the witness when you are asking them questions as to the difference in their account to yours. You will hear this called "putting the case": you have to put your case to the other side's witnesses, so they can comment about what you say happened.

If you "put your case" you will be able to comment upon the difference in accounts in your closing submission.

if the tribunal were to make findings of lying against a witness in a material matter, the other party could apply for costs