It's only been 2 weeks...

I'd argue that you don't have to mention this job at all. When asked why you're job searching you can explain why you left your previous position.

If for any reason you can't omit a job from your work history no matter how short (locale, the type of job you're applying for, etc.), you can be honest without going into details:

I'm leaving my current job because the position changed significantly after I started.

This is true: you took the job because you were expecting a raise and now that raise isn't going to happen. But you don't have to mention that the significant change was about compensation.

This is a common enough situation that they ought not to press you further.

It's only been 2 weeks...

I'd argue that you don't have to mention this job at all. When asked why you're job searching you can explain why you left your previous position.

If for any reason you can't omit a job from your work history no matter how short (locale, the type of job you're applying for, etc.), you can be honest without going into details:

I'm leaving my current job because the position changed significantly after I started.

This is true: you took the job because you were expecting a raise and now that raise isn't going to happen. But this wording allows you to avoid saying it was about compensation if that's what you're concerned about.

This is a common enough situation that I think some employers will leave it at that. However, it's been pointed out in the comments that others will worry that what you consider significant might be normal to them.

So if you're asked to elaborate, you'll need to say that the significant change was to your compensation. Borgh and Bilkokuya have already suggested alternate scripts in the comments.

It's only been 2 weeks...

I'd argue that you don't have to mention this job at all. When asked why you're job searching you can explain why you left your previous position.

If you're in a region where you can't omit a job from your work history no matter how short, you can be honest without going into details:

I'm leaving my current job because the position changed significantly after I started.

This is true: you took the job because you were expecting a raise and now that raise isn't going to happen. But you don't have to mention that the significant change was about compensation.

This is a common enough situation that they ought not to press you further.

It's only been 2 weeks...

I'd argue that you don't have to mention this job at all. When asked why you're job searching you can explain why you left your previous position.

If for any reason you can't omit a job from your work history no matter how short (locale, the type of job you're applying for, etc.), you can be honest without going into details:

I'm leaving my current job because the position changed significantly after I started.

This is true: you took the job because you were expecting a raise and now that raise isn't going to happen. But you don't have to mention that the significant change was about compensation.

This is a common enough situation that they ought not to press you further.