The term 'Run Up the Phone Bill' refers to a situation in which someone talks on the phone for an extended period of time, resulting in a high phone bill. The crossword solutions for this term are YAK (3 letters), GAB (3 letters), and YAP (3 letters). YAK is a verb meaning to talk or chatter at length, GAB is another verb meaning to talk incessantly, and YAP is a verb meaning to talk rapidly and continuously. All three words refer to talking on the phone for an extended period of time, which can result in a high phone bill.