Tax Credit Renewal Childcare Costs Frustration

Hi All,

I've just called up to renew my tax credits claim and when I asked the woman if I could update my childcare costs she said the system told her not to as a letter was sent to me on 25th April. I haven't had the letter and she wouldn't tell me what the letter said......
Has anyone else had a similar problem who could give me some ideas as to what this letter could be??
Many thanks