Free Open-Source Software or tool to conduct sms phishing/ smishing attacks against company employees

I work at a relatively small company (less than 200 employees) and management has asked us to try to conduct sms phishing attacks because our new hires keep getting the targeted "hi this is your CEO, can you help me with something?" texts. I'd like to be able to run a smishing test against our employees, and was wondering if there were any free, reputatable programs to accomplish this. extra emphasis on free as we already have a security training …

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