Anyone tried one of the cordless models with link to cell? I have a Panasonic set and we have 1 iphone 4s and one I5 in the house. We have them both linked and most of the time they work fine but sometimes the 4s more then the 5 has so much static or crackling that you can not hear what the person on the other end is saying. The cell phone is within 10' of the base. Seems to be no reason this happens just random.