The shaft on the wastegate of my turbo is seized and doesn't Move, how can I fix this?

This will have to be dismantled and over hauled, I am here to tell you if you try this at home the turbo will end up in the rubbish bit, I have been in this industry over 35 yeas and work on many turbo engines, I will not attempt any turbo repair work, they should be done by the professionals that deal with there jobs, they have the equipment and the expertise to get it right the first time, often with turbo's there is no second chance.