Students who lease phones, for 12 months will only pay 9 months rental cost. Also, students renting or buying phones from AT&T can have them fined for free at the AT&T store-at 45 Prospect St., Central Square.

* HSA sells a one-piece touch-tone phone with a 12-month warranty for $15.99. HSA's Science Center desk will be open 9:30 a.m. to 4 p.m. today and tomorrow, and will also sell the phones from its Thayer Hall basement office next week from 1:30 p.m. to 5 p.m.

* For local calling, one must deal with New England Telephone. They offer metropolitan service, which takes in 44 exchanges in the Boston area at $16.75 a month for a touch-tone dial tone and $16.15 a month for a rotary-set dial tone. For contiguous service--access to Cambridge and all the cities that border on Cambridge--studdents pay $11.20 for touch-tone at d $10.60 for rotary.