The Consumerist notes that some former Adelphia customers who are now under the Comcast umbrella are being charged the $3 rental fee even if they own their modem. Comcast says they're having a hard time determining if users rent or own their modems on account of poor record keeping (we assume on the part of Adelphia). Some users are being told there's nothing Comcast can do unless they can show proof of purchase for the modem.Proving to Comcast that you own your modem has popped up as an occasional but consistent issue in our forums for years. This isn't an Adelphia issue, as customers who've always been with Comcast face the same problem. While such complaints are common, most customers say Comcast is usually quick to fix the error when you bring it to their attention (though users say the erroneous charges sometimes return later). It's always a good idea to double check your bill if you've purchased your modem elsewhere.