If you use the Java Card Classic Development Kit 3.0.5 to convert your application, it will by default assume that you're using the 3.0.5 API in your application and create a CAP file importing packages containing classes as defined in 3.0.5.
Then, when loading this CAP on a 3.0.1 card, the linker will detect that your application is importing package versions as defined in 3.0.5 and potentially using classes/methods that didn't exist earlier in 3.0.1.
In your case, you have to specify that you're targeting a 3.0.1 platform. To do so, you can either use the 3.0.1 dev-kit, or still use the 3.0.5 development kit, but provide the export files from 3.0.1 or even better the export files provided by the card vendor. In the eclipse plug-in, I recommend to create and configure a specific Platform that can be used for this purpose and still keep the default one for 3.0.5