I'm with Celcom since 2008... drop call is normal with celcom... but now many issue with celcom even after they SMS for infra upgrade in my place...
- drop call (normal issue with celcom)
- Slow 4G this year 2016 is worst celcom speed compare to last 2 year in LTE speed
- drop signal from 4G to 3G, H+ till H(never had this issue last year)
- all of my location celcom data speed, call drop & line drop is getting worst( Setapak Sri Petaling Shah Alam)

Gonna change to other telco later

I already buy umobile prepaid.... speed is good......... the only throwback is umobile seem to block CSGO competitive game... so i have two option.... buy celcom prepaid..port my postpaid celcom to umobile P98...or buy other telco prepaid yellow or green just to cater my CSGO data...and use umobile as my main telephone line...