口头一些的说法(聊天说的）：
I'm so sorry about last night.I forgot to tell you that my landlord often unplug the modem at around 11pm,that's how i got disconnected.I'm really really sorry.
书面一些的说法（写文用的）：
I want to apologize for last night.I was unable to come online due to the fact that my landlord disconnected the modem cable daily at 11pm.I am sincerely sorry.