Social Security

Terry,
I waited until my full retirement age to start collecting half of my ex-husband’s social security. I will be turning 70 in September. I received a letter from Social Security saying that when I reach 70 I should take MY full amount because it will be more than half of my ex-husband’s. I called to ask about this the person on the phone set up a phone call for me with a Social Security professional on June 23rd. I was also told if my ex-husband passes before me I can call and change the amount and start collecting surviving spousal benefits. Is all of this true? If not, could you please tell me what would be best for me to do.