Hi @plindqui,
The simple answer is that you'll most likely need to contact your school/institution Canvas admin team (usually in the eLearning / IT / Digital Education areas) to fix this for you.
Your colleague most likely crosslisted the sections into a single course for your convenience, but unless your school has a very rare setup, de-crosslisting isn't something teachers will be able to do on their own for some very technical reasons.
I hope this helps answer your question, even though I know I'm redirecting you a bit.
-Chris
