Should I pay the settlement offer or no?

Hello all!

So I had an issue with Fido. My brother cancelled his plan and I forgot that we were still paying for his phone. I was on a payment plan but had a baby and totally forgot to follow up.

Since then they’ve taken me to collections. I’m soooo upset because the amount they took doesn’t reflect how much I’ve been paying.

I’ve now got a 50 percent settlement. Should I pay it or pay the full amount. How will this affect my credit score.