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I hate to say it but in my research the blocker you describe is a scam associated with what appears to be targeted phishing. In this case, they call many times from different numbers, and send a call blocker hoping you (or someone like you) will download and install. The phone numbers they have range in the same 800 block, so it is likely they bought all the numbers at the same time.
my best recommendation here, though it is a big pain, is to change the card number, and tell the bank about the fraudulent nature of the transaction (or company trying to make it)