Worst service

I have had the worst experience and actually at my wits end, I took a cellphone contract which I needed to have already 3 weeks ago to help with my daughter as they stole her phone and certain things they can only study in the WhatsApp groups ect, DSV has twice now been to my house to deliver after scheduling a time between 8 and 10, on both occasions they only came and hour or 5 hours after the scheduled time where I was forced to leave home after arranging to have off at work for that 2 hours on both occasions they have not committed to the times and found my unavailable as I'm on the road, explained the 2nd time what the situation. Is they can't come at different time and again. Only got to me after 11am a 2 hour later delivery as supposed to keeping to the arranged time, now they want to reschedule for Thursday or Friday, unfortunately I cannot get 2 hours off again for the 3rd time what do they advise I tell my work, why again and then you can't trust them with time, so how to resoIve