Repetitive collection calls to clients who pay on time

Citimortgage has begun making repeated monthly collection telephone calls during my home loan's grace period (before the payment is late). It would be bad enough if only one call was placed, but citimortgage leaves multiple messages on my answering machine within hours of each other. I realize that times are especially tough for Citimortgage right now, but this latest issue only adds to the list of annoyances I have experienced with Citimortgage. I will certainly remember these when shopping for mortgage products in the future. Note: I've never missed a payment or had one processed outside of the grace period. Why does Citimortgage treat good customers this way?