any way to edit AT&T APN without rooting? need help ASAP!

Thanks for reading I need to tether with my HTC aria from att. I am now using it on straight talk MVNO. all ofther data features work perfectly, but when I turn on my wifi hotspot it gives me an error to "contact att.com or dial 611 if you want to use tethering feature"....other people use iphones and other gsm phones with straighttalk and have no problem. The default att apn configuration has a little lock icon on it and I need to delete that apn so the other straight talk apn will not be affected :-) thanks for looking and thanks in advance for your replies...Rich