我要投诉。你们寄给我的帐单错了。况且，这也不是第一次了。

I have a complaint to make. The bill you sent me was incorrect. What's more, it isn't the first time.

youdao

我写这封信要投诉你们的售后服务。

I'm writing this letter in purpose of complaining about your after-sale service.

youdao

我写这封信要投诉你们的售后服务。

I'm writing this letter in purpose of complaining about your after-sale service.

youdao