Wealthtrust does not charge anything for Switching of Regular plan to Direct plan. However, there you need to keep in mind the Exit Load and Tax impact. 
Exit Load: Check whether your investment is beyond the exit load period. For example, most equity funds have an exit load of 1% if you switch/sell within 1 year of purchase. Hence if your investment is less than one year old and if you switch now you would need to pay 1% exit load on switching. In this case if your investments are more than one year old there will not be any exit load. 
Tax impact: A switch transaction is considered as a sell and a buy for taxation purpose. Hence the gains made at the time of transaction are subject to tax. Read our mutual fund taxation blog to know more.