Phone call recording

Hello sir I wish to ask the is phone recording is legal? 1) for my customers sometimes our customers are backout from the fixed payment terms and from the fixed rates that why if we do the recording, can that recording can be presented before the court? and will it be accepted a legally fare? 2) in case for wife recording. some times wife talks bad words and other bad words by wifes relates. is recorded so can that recording is legal to present before courts. 3) recording in court campus is legal?