The best way (except from moving to a provider where you have ssh access) is to use compose locally and then upload also the whole vendor directory. This will also upload the new vendor/composer directory. In that directory is the autoload part stored. The content of that directory is used to find the classes. Without that it shouldn't find the class you want to use.

Thank you Tobias for replying. I have installed the package locally but l can’t replace the vendor folder as the project has been worked on by another developer. Is there a way to directly edit vendor/composer with the changes that was made locally to the file.if yes how do l achieve this.thanks

I should suggest use git or any other version control system. Where you put you composer.json and composer.lock file. Each time someone need to upload a new version that person can pull the latest version, run a composer install and upload the vendor directory.