To be honest, the enquiry service is known for giving incorrect information, including telling people a decision has been made when in reality, the application hasn’t even been looked at yet.
It may be that they were correct and a decision has been made, but given that it’s been so long since they told you that and you still haven’t received the official decision made email from Sheffield, I would assume your visa has not yet been processed.
Normally, the visa will be issued and mailed out either the same day or within 1-2 days of receiving the decision made email and UPS tracking emails from Sheffield.
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