Okay this could be long so bear with me...
Dd is 7 and generally has a great relationship with her dad. He lives just around the corner from us (me, dh and ds) she sees him every sunday most of the time and he will see her on the odd occasion during the week if he isn't working. She absolutely worships the ground he walks on.
Bit of a backstory now, we hd dad when we were very young and he was always in and out of our lives. One minute he was around and then he would disappear for weeks at a time for no reason, it messed me up mentally but i shielded dd from it as much as i could and it never caused her any harm as she was so young and it was what she was used to iykwim?
Anyway me and exp get along fine for the sake of dd although it has caused a few probs between me and dh in the past it all seems to be sorted. Week leading up to xmas we had been discussing presents and when he was going to see her etc. Initally he says xmas eve for a few hours to which he had to cancel last min (well he rang at 8pm to see if he could pick her up in half an hour but she was in the bath getting ready for bed so i said no esp as he originally said he would see her early evening which i assumed was about 4-5pm) so then he says don't worry i will have her all day on the 27th as he was xmas and boxing day and he had promised dd he would see her then.
27th comes and i've not heard from him so send a text to ask where he is, no reply. Tried ringing and was completely ignored, went to his house and even though his car was there his dad says he isn't in
Have sent texts everyday since, rang several times and have been ignored every single time. No explanation no nothing. Dd is absolutely devastated and i have witnessed behaviour from her like i never have before. I've found her sobbing her little heart out in her room asking over and over why he can't be bothered to see her. He does tend to let her down every few months like this and not see her for a couple of weeks and i guess now she has just had enough of it and recently he has pulled his finger out and made more of an effort so even i am shocked he could do this at xmas. She keeps saying she has a funny feeling he never wants to see her again and its breaking my heart to see her so upset about it. She keeps telling dh that her dad is the most horrible dad because he never keeps promises and he can't be bothered with her 
I'm not really sure how to explain it to her as even though she is quite grown up she is still only 7 and is quite clearly very upset. I've told her its fine she has us here but she keeps asking me to go round and see if he is in and making up excuses for him as to why she hasn't even had a phonecal from him to wish her a merry xmas for example that his dog is playing up or he is poorly etc.
Thankyou if you have got this far i did warn you it may be long! any help would be appreciated!