To call somebody and to phone somebody are used in informal English. To ring somebody is used in informal British English. To telephone somebody is only used in formal English. There are also other expressions like: - to give somebody a phone call - to give somebody a call - to give somebody a ring (British English)
call / phone You should call/phone your mother. Please call/phone me when you arrive. You can call/phone me whenever you want.
ring You should ring your mother. Please ring me when you arrive. You can ring me whenever you want.
telephone The police telephoned the suspect but could not reach him. The secretary telephoned to say that she was late. Sarah telephoned the insurance company to renew the policy.