Open Question: Are there additional premiums with single premium policies?

Last year I purchased two single premium whole life policies for two of my children. They were 5 and 1 at the time and I paid about 4800 each policy. One year later I am being sent a statement for annual premium of $365 for eac child. When I questioned my agent he stated b/c the economy is so bad the insurance is asking for additional premium. Is this right or can this happen. Please help