Have you told them why you don't want contact anymore, @TurnUpTurnip? Often, people who go NC - and they're quite entitled to, for even the most spurious of reasons - simply stop communicating/"vanish". And the other party is confused, doesn't understand that the problem is them/their behaviour(s)... so they continue to try to communicate.
My maternal grandmother, aunt and two uncles went total NC with my mother a few years ago - and she didn't understand that it was because of her behaviour towards them/their families. She pressed for contact with them, citing her mother's age (she's in her 90s, but totally "with it") and alleging kidnapping. It took the police telling her, after she'd asked for a welfare check to be carried out, that they didn't want contact anymore before she'd drop it. Why? Because they're all still in contact with me/my children. That it's my mother's behaviour and attitudes at fault never occurred to her - despite my being very LC and my two brothers NC with her for the same reasons her mother and siblings cite. She simply cannot understand that she is at fault, even when it's spelled out to her in simple terms, but the communication "we're NC with you, for these reasons, please respect our decision" worked. Well... for now. I fully expect my mother to start trying again when my grandmother dies... if she's even informed. I know I'll be told, as will my brothers, but wonder if my grandmother's oldest child will be.
If this is a parent, or inlaw, OP, then the gifts for your children may even be their trying to "be the better person". Any issue is with you, not their grandchildren, if you see what I mean. Which is ludicrous because you're the parent and right now, it's up to you whose gifts they receive. But if you haven't already communicated the "why" to them, maybe it's time to?
