call up打电话召集，召唤
call on呼吁，约请，拜访
call on
1) 拜访
I'll call on him tomorrow.
明天我去拜访他.
2)号召呼吁
3)邀请
call up:
(1) 打电话给
make a telephone call to
[例句]
Call me up tomorrow：my telephone number is 536291.
请明天打电话给我：我的电话号码是536291.
(2) 打电话
make a telephone call
[例句]
This morning someone called up from downtown and asked to see me at two o'clock.
今天早上有人从市里打电话来，要求在两点钟时来看我.
(3) 唤醒
arouse from sleep
[例句]
Shall I call you up at six tomorrow morning?
我明天早上六点钟叫醒你好吗?
The doctor was called up three times last night.
昨夜医生三次被从床上叫起来看病.
如何区分callup和callon
callup释义：
n. 征召（服役）召集
例句：
Little implied that one reason for being non-committal is the repercussions a callup would have on his current club.
小暗示不确定的一个原因，是叫人上来对他的球队所造成的影响。
callon释义：
n. (Callon)人名(法)卡隆
例句：
If the aliens really are landing， this latest picture seems to confirm that their first port of callon Earth will be Russia.
如果外星人真会登陆地球，那么这张最新照片似乎可以证明他们的首个著陆点将会是俄罗斯。
