Allow me to rephrase your question: You contracted with a pool company to install and finance a swimming pool. The installation or materials were defective, and presumably after asking the pool company to fix the defects, the company refused to or did so inadequately. As a result, you stopped making payments three months ago in an effort to spur the pool company to make adequate repairs. It has not done so, and you learned recently it sold your collection account to a collection agent.
Regarding your first question, an original creditor is not required by law to notify a debtor it sold the debtor's collection account to a third party. Therefore, I do not see any illegal act here.
Regarding your second question, you have three options. First, you can do nothing. Some collection agents make somewhat half-hearted attempts to collect debts. Others, however, are much more aggressive and will use all legal means available to pursue a debtor. You mentioned you are in Texas. See the Bills.com resource Texas Collection Laws to learn more about your rights and liabilities as a debtor in Texas.
Second, you can file a breech of contract lawsuit against the original creditor. As distasteful as this may sound, this was your first best option when the pool company installed the pool in a defective manner. You should have continued to make the payments, and then filed suit.
Or finally, you could have filed the suit and then stopped making payments after filing your complaint.
The original creditor has the right to sell your collection account. It promised to build a pool for you if you paid for the pool using installment payments. You have the right to file a lawsuit against the creditor if it fails to build the pool according your state laws. You can, as you did, refuse to make payments. However, the pool company has the right to sell or assign your debt to a collection agent.
Taking matters into your own hands has not caused the pool company to change its behavior. It is time to consider asserting your legal rights. Consult with an attorney in your state regarding your defenses to a possible lawsuit regarding the debt. Also consider filing a breech of contract lawsuit against the pool company for installing a defective pool.
I hope that the information I provided helps you Find. Learn. Save.