"They wouldn’t give me my money back.".What is the meaning of 'would' in this sentence?

I am learning model verb 'would'. And one of the sentences I am not being able to understand. Here is the sentence "The CD wasn’t working so I brought it back to the shop but they wouldn’t give me my money back because they said the box had already been opened." What is the meaning of would in this sentence.

In most uses will is a modal, with a variety of meanings, "futurity" being a prominent one. Would can function as the past of will (Eg "I will go" -> "He said he would go"), but also has its own range of meanings separate from will.

But in origin, will was a full verb, meaning "be willing to". It still has that meaning sometimes (though syntactically it is still a modal). Would can act as its past tense in this meaning

So a direct paraphrase is They were not willing to give me my money back, or more coloquially, They refused to give me my money back.