I have used both online and calling the regular number and if I did not get an email confirmation I sent one to them asking for one. The site says
E-mail Reservations
Request or cancel reservations 24 hours a day, 7 days a week
Use a credit card to process your reservation
Receive confirmation of your reservation within 2 business days. :yes: like I said above if I do not get confirmation I email
https://www2.tpwd.state.tx.us/busine...52Findex.phtml
I choose other and list my dates and park and ask for a confirmation
The regular number is 512/389-8900 weekdays