In account management click on configure/portfolio columns, turn on liquidate last. Then right click on the security in account management, expand all the options, select liquidate last.
You do not need to speak to anyone to take large sums of money out of interactive brokers. Just fill in the funds transfer form on the account management website.
You pay IB to clear your trades plus the exchange at the moment. Members do not pay the exchange fee but do pay their clearer to clear their trades. Look on the IB website and it will break down the saving.