yes you can .

if you are using prepaid , you are required to go to your operator like maxis center . 

there will be a small charge if you need to re-active your number back @>@

i prefer you better go earlier before TOO LATE @.@

i did once before , i not sure how much it charge because that was 3 - 4 years ago ..

right now i just switch to postpaid plan and i highly recommend you to register yourself as a  postpaid user , they are a lot cheap plan right now  which including the internet and call ...