I live in Pa. I got papers to go to court for credit card debit. I made a settlement agreement with collection agency. I have already made payments etc. I have the agreement in writing. I reply to the court saying I was going to to defend myself. A couple of days later I got a call from the collection agency saying I was NOT to reply to court, and why did I. They also said that I was NOT to show up for the court date or that the settlement agreement would be void. I have read the papers and they say nothing about if I go to court the agreement is void.

At a lost

Ignore the collection company and turn up at court.
Even if it's simply for the judge to strike the case out as you are paying, NEVER trust these people. After all, they are only interested in getting the debt paid, by any means.
They will most likely attempt to get a default judgement against you and then enforce it!

Should I call the collection agency and tell them I will be there?

No, you just show up since you can bet they will be there.

Please don't talk to them on the phone or trust them,

If you have an agreement in writing, please take it to court with you.

What they want is for you not to show up, so they will get a judgement by default. Then if you break the agreement by one day they can start a garnishment or more.

They told me on the telephone that they did not want to travel to go to the hearing. They are about 3 hours away.

Do not believe anything they say. The only time you should not go to court is if the judge, the court clerk or your attorney says not to go. Never ever believe the other side.

What happens if they do not show up?

What happens if they do not show up?

Ask the court to dismiss their claim with prejudice

Update:
I went to court this morning. Waited for 15 minutes for them to show. And they were a no show. They called me to the counter and said the case was "dismissed without prejudice" . And that was it. Thank you all for your help in this matter.

Congratulations. But you should still keep making the payments according to the settlement agreement you made with them.

Dismissed without prejudice means that the plaintiff can re-file the case. If you don't keep up with the payments they'll re-file and submit the agreement as their proof. But right now there is no judgment against you and as long as you keep making the payments there shouldn't be a judgment.