Upvote:5
Your question cannot be answered with one single strategy, since it comes down to a negotiation with the consul and their estimate of the situation. From the description you gave in the comments, here some thoughts:
They tell you that you should have a "work visa" and at the same time, they tell you that your return to your home country is not guaranteed. This tells me that you have to convince them that you are not willing or able to immigrate, but really go there only for a short time. They are trying to force you to apply for a work visa, since they assume that you will go to Spain for permanent work instead of only a short term training. The Spanish government is worried that you are not honest in your explanation and, instead of just going there for a short time, "disappear" in the country and seek permanent employment and residence in Europe. If you apply for a work visa, you essentially would get a permit to do so.
So in essence, they ask you to apply for a visa that lets you do what they think you are intending to do, instead of what you are telling them.
In principle you need to make the consul feel safe that you do what you say. The more information you can deliver, the better. Your goal would be to prove to the consul that you either have a binding need to return home, no reason to stay in Europe or that you are doing something that has happened before without problems.
If your can show that your company and/or the client is a large, international corporation, it's better.
It will also help if your client can prove that they have invited people from other countries with similar immigration risks (such as Indonesia, India, North Africa etc) and all of them left the country on schedule.
Another option would be that you can prove to the consul that your income is high enough that you are not a person that would likely try to illegally immigrate into Europe to find a job there. For example, if you can show that you are a higher ranking manager with a significant salary and career in the Philippines, your chances are much higher than if you are a factory worker.
You could also provide the contract that was made with the Spanish client. If the contract clearly lays out the training requirements or such, the consul might understand that this is not an immigration scam.