800 sounds cheap...
lawyer is a must=== fully redemption from DBS and taking from another bank--- but be careful, bank charges still applies-- better check with DBS how much you will need to pay, I paid at about $1,300 ...
so total switching cost will be ard 2k--- and if you are taking sibor or sor linked package, there is only 4 days in a year you can fully repay your loan without penalty, which is one day the interest changing day...better check with the lawyer
It is much more expensive than you would expect to switch a bank...