Do I owe the money back or not?

I have a lifelong chronic illness and have been getting esa for the last three months.

Due to a lot of personal issues at the moment I decided to end my claim, it was on a monday, on the wednesday they paid me.

I called them to tell them I ended my claim and then got paid into my bank account, the lady I spoke to checked and told me she didn't think it was an overpayment and if it was I would owe a very minimul ammount back, the phone ended up being cut off so I called back, went through it all again and was told by someone else that I owed £70 and that I would get a letter informing me how to pay it back.

I have had no letter and the money is still in my bank so I decided to call back to be told I didn't owe anything at all as it was a normal fortnightly payment.

I am a bit confused as I am still none the wiser if I actually owe anything back to them because I have been told three different things, how do I get this sorted out as I don't want to spend money that isn't mine.