It is understood that sometimes IT service providers need to build capabilities if they desire to sign on a client who requires certain skills in much the same way companies need to build such capabilities in-house when moving to new or different technology. However, what Giles said speaks to the fact that sometimes such service providers claim to have certain capabilities even if that’s not factually true.
My hope is that your new employer has a path already for you to learn these skills if they are hiring freshers or professionals who do not have such skills already to provide these services. This can be formal training from the vendor or an in-house course you will go through when you begin employment based on the knowledge gained from other professionals or education services.
If your employer didn’t require you to have such skills to be hired, it is their responsibility to provide such training to have you become enabled to function in the role you will perform. Honesty in both the employee-employer contract and the service provider-client contract is key to being successful.