humana misinformation Nationwide

We purchase a new medicare supplement plan for my mother in 12 of 2015 but did not cancel our humana plan until we had confirmation of new policy in our hand. On 1/12/16 we contacted humana to cancel the policy and were told policy would be cancelled, we asked at the time if we needed to send in a letter to cancel were told no. We contacted humana on 2/3/16 to confirm the policy had been cancelled and were told that it had not been sent to the disinrollment department but they would take care of it. But our big concern was that no further withdraws from my mother account would acure but it happen. Now we have been told we did not send in a cancellation letter. So my sister called and told them we were never told about a cancellation letter and she told her that was old shcool and let it out that they knew we had taken another plan but then put us on hold and came back to tell us they needed a letter of cacellatoin and we should get your february money back but not your january payment not even prorated even though they knew that we had another plan