When I was taking master's degree, I attended a one year's program in affiliation between my university and a commercial research institute. At that time, on the contract, I was placed as visiting student. Then after graduation, I extended my contract for half a year. And the renew contract shows that I was under the agreement of visiting researcher. I put visiting researcher for this whole 1.5 years' experience on my CV because visiting student seems not strong enough. Is this right to do? I didn't notice this problem until I found that my former supervisor always referred me as visiting student and I've sent out several Ph.D. applications. Is this a kind of cheating that I call myself visiting researcher?
Do you have a copy of your renewal contract? If you don't, you should ask for it since the contract is with you.
Ask your supervisor if they are willing to be your reference. Point out to your supervisor that you are referred to in the contract as a "visiting researcher".
The next time a prospective employer asks you for a reference, contact your supervisor and remind them that you worked for them as "visiting researcher".
List your position as "visiting researcher" since you have the renewal contract to back up your claim.
Having said that, the description you give of your duties will give away what you actually did. If all you did was say washing test tubes, no fancy job title is going to make up for a lousy job description.