Dafny - Call methods inside if statemnts?

Like the title says I would like to call on a method that modifies some variables inside an if statement of another method, such as:

method A
...
{
    ... // Modifies some variables
}

method B
...
{
    ...
    if(statement){
        A();
    }
    ...
}

This doesn't work since Dafny won't allow non ghost methods to be called in such a manner. What would a workaround to this issue be?