Full Metal Alchemist (between mustang and hughes)
Evangelion (shinji uses a pay phone in the first ep, and theres an Asuka cell phone in there somewhere)
Loveless (cell phones, Ritsuka is constantly looking at it)
Fruits Basket (Tohru uses the school phone atleast once, and theres Sugure's agent constantly calling him... and Ayame calls Hitori atleast once...)
Onegai Teacher (im sure that theres phone use atleast once... i cant remember when exactly)
His and Her Circumstances (quite a few im sure

)
Ouran Highschool Host Club (theres atleast one or two instances, most notably the ep where Haruhi gets a job and Tamaki is trying to hunt her down)
Princess Princess (phone is used a couple times..)
Spiral
Cardcaptor Sakura
D.N. Angel
99% of my collection....
actually just about every anime i can think of (save for stuff not set in modern times) has a phone use atleast once