Mean you change to others operator such us maxis to u-mobile by maintain existing number  

1- Yup, can MNP from prepaid to prepaid.
2- We will proceed the MNP after you receive the SIM card through postage, so whole process may take more than 1 week, depend the postage speed.
3- About coverage, you can give us the address, we help to check first. When no coverage, 2G will use Maxis coverage.
4- Call rates is 18 sen per minutes and SMS 8 sen to other operator