Other replies have well covered the reality of the situation. Except ldij downplaying the missed phone calls as not that big of a deal. You are just plain wrong to deny the phone calls, there's no excuse to deny them, period. But, I did want to respond to a few other things.
That's not really here nor there, but since you shared this info about your particular situation, it makes you even more wrong for doing what you could to deny a move to have a visit by blocking phone call from Dad to kids.
By your own admission, this was the exact reason you denied the phone call. So even in advance of Dad articulating a desire for a visit, you nipped it in the bud farther back than that by not even allowing a phone call, a deliberate attempt to alienate Dad from kids.
The court order spells out the MAXIMUM rights Dad gets. It also spells out the MINIMUM rights you must allow. So this idea Dad isn't "abiding" by the court order .... that's neither here nor there for the purpose of the discussion of whether Dad is allowed to talk to the kids when he DOES call. You are not the first CP with a NCP that doesn't use all of their allowed time. That gives you NO right to act unilaterally to block ALL time (phone/visits) just because he misses some. Your right is to take him back to court to have the JUDGE limit time if you think it's justified. Your actions are 100% wrong.
I don't know why you injected that you could use a few hours to get things done. It's not about you. As far as his country not being a signatory to the Hague, frankly, I wouldn't have had children under these circumstances, but you did and cannot use that as an excuse to do as you please. Further, you already have an existing CO and if you are so sure that you aren't protected currently, you can go back to court and have your fears see the light of day and be reasoned with there, not holding all the cards yourself. So far you have engaged in actively alienating a father from his children. Maybe he shouldn't give up so easily, but you have denied him even phone access to his children for 2 holidays in a row (Thanksgiving, Christmas) and apparently won't be happy until Dad ceases contact altogether. We didn't even hear about the Thanksgiving denial initially, that came out only after this thread was well underway. I recently found a buyer for the marital home and had to deal with him (first time since March) and after realizing I needed him to sign the contract, he refused to sign and gave a really hard time. He called yelling at me the Wednesday before Thanksgiving (what is it with him and holidays) and threatened to take me to court again about the children, find a better lawyer (he doesn't realize his lawyer was pretty damn good considering the circumstances), never sell the house, etc. I tried explaining they hadn't spoken to him in a year and he needed to be consistent - not just jumping in and out of their lives. He hung up. Fast forward to Christmas morning and he called and left a message on my voicemail saying Merry Christmas and have the 'pickney' call him (it's a slang word for children in his country). I didn't comply with his request. It's as though you just don't "get it" and are sitting back blaming Dad for no contact when in reality Dad has TRIED and you are the reason he hasn't gotten the contact he's legally allowed.