You have to call ATT.... tell them you are hearing impaired and that it takes you a while to hear your phone ring and also that it takes you a bit longer to get out of your chair to get to the phone.
Of course, don't sound obvious and say it all upfront at once! Even tell them its your grandmothers phone and SHE is OLD.... They can adjust it!
Have 4 phones on my AT&T account. Had AT&T set them all to max ring time, which is 27 or 29 seconds. Gets me 7-9 rings. Great. Careful if you call AT&T and make any feature changes though--they always seem to set ring times back to defaults, so you need to make sure they set them back.