claim under the service agreement

Good afternoon, I have a question about a service agreement between a Russian citizen and a company from Vietnam.
The essence of the claim against the company is that, according to preliminary agreements, certain conditions were discussed in the correspondence, but only the name of the service was added to the text of the contract without specifying the stages of its provision. The service was provided improperly.
Whether an agreement in correspondence takes precedence over a written contract.in