Add/Remove Data and Column from a SQL Table, then replace column.

Hi, I need a script in SQL server management studio to delete data from a column or remove the column all together and then replace it. Format below. Database : CurrencySystem Table : tblDetails Column : ChannelA No of Records (bigint, null) These are the details, how to delete all data from the column, or remove column and then re add? Possible two columns A & B. Thanks