Scheduling a new internet installation time

Hi o2 people,

Today I had the scheduled visit from technicians to install my o2 internet. However, they could not do that since the telephone distribution of the house was behind a door which was locked...  I asked about this several times in advance from my landlord and he promised it would be open, and even told me it was open today. 

Nevertheless, I now need to schedule a new appointment for the technicians. How could I do that? 

I tried to call the number given in an email I got this afternoon from o2, but I did not manage to reach any English speaking person. Also tried the live chat about 20 times but no answers and it ends up timing out. I will ask my coworkers if they could make the call for me to the hotline, but before that I wonder if I could get help from here?

Thanks!