In the morning, I received a phone call from someone claiming to be from the public security bureau. They asked if I was XXX and if I lived at XXX. I replied yes, and they claimed I was secretly accessing VPN and asked me to come to their office. I initially thought it was a prank, and asked for evidence to support their allegations. They told me I didn't need to deny it and that my personal information would not be revealed in such a situation. I was eventually convinced and agreed to go, explaining I was an engineer who occasionally accessed VPN to gather information. They claimed to have evidence of me using foreign social media accounts, including Twitter, which I denied. I offered to cancel my account but was told it was part of the procedure. I was asked to come in the next day after work, which I reluctantly agreed to. Does anyone have any experience with similar situations or advice on how to handle them?