Verb conjugation of "telefonare" in Italian

The billing of additional working hours is not justified, since it was our request to download the software and wait for the new version. They have admitted the error of the translation.
The last sentence is the hardest in the entire series. Writing may bore some people, but it is considered the best training in language learning. It is a skill that can lift you from intermediate to advanced level. Do not neglect it.
If I'll have the time, I will visit sometime, perhaps you can write me an email in English. I will be correcting it and hope not to discover any errors there. In which city do you live?