My question involves landlord-tenant law in the State of: Texas
Hi! I am currently a college student dealing with my first landlord. I moved in to an apartment complex about two years ago with a 6 month lease, then renewed again for another year. During this year they sold the complex and switched management companies, changing the payment portal several times. The new portal didn't work for two months, requiring tenants to bring money orders to the office with only two days notice. I continued to pay my rent throughout the lease, using three different online portals and paying by money order twice.
Each time a new portal was opened my balance would either be zero or some random amount not even the amount of my monthly rental payment. I called the office several times and they would eventually fix it.
Naively, I did not keep proof of my payments on the second portal because I assumed that the new company would keep the portal operating throughout my lease and the payment confirmations were there.
I moved out at the end of my lease with no issues except for a $6 cleaning fee which I paid because I did not have a security deposit. Then about a month later they sent me a statement saying I owed three months rent and sent the "debt" to collections. I just received the letter from collections in the mail yesterday. I know that I need to dispute the debt immediately, but what happens after that? According to what I've read they will need to provide proof that there is a debt owed, but I do not understand how they will intend to do that. I really don't want this affecting my credit score, or my dad's credit score as he was my cosigner.

