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In the old, obsolete days of courtesy, it would have been insulting and impolite for a dinner date to answer a phone call during the meal. It would have a date-ender if he/she reached into his/her purse, grabbed his/her phone, and dialed a call to someone, just to chat.
But really, a telephone has always been an instrument of rudeness. Unless you're sitting at a desk, and your job is to answer phone calls, any phone call is an interruption to the person being called, a message that whatever he is doing has to wait because the caller has to communicate something NOW.
Probably in that context, you can't complain too much about telephone rudeness. Rudeness is part and parcel of telephones.