We did some work for a costumer, and she was upset because we did not send the cleaning company, she wanted but it was not in our contract or scope of work. We were just doing her a favor because she had an accident. After that she stopped answering our calls, text, messages and emails. she still owes a percentage of contract plus two supplementals
You may be eligible to record a Mechanic's Lien to secure the debt owed. Check out this handy guideline for information: https://www.levelset.com/mechanics-lien/
You are not required to perform work outside of your contract to be paid, unless you amend or alter the contract. For that reason, I recommend that any change to the contracted work be done with a change order signed by the homeowner and indicating any adjustment in price caused by the change. The customer typically will not have legal grounds to withhold payment because you did not do something you weren't required to do.
If the amount owed is fairly large, I suggest you contact an attorney to help you with collections (a mechanic's lien if appropriate, a collections letter, litigation if needed, etc.)