奴隷の分際で王に敬称で呼んでいただくなど……恐れ多いことです。
The slave asked the king to call him by his first name instead of using his surname + "san", so the king asked him why. Then, the slave answered the above sentence.
I don't understand the function of the particle "に", because it seems to imply that is too much to call a king with honorifics, although with the context, it's exactly the opposite: to call a slave with honorifics. Is "に" linked to "いただく"?