Same “new” router with same “old” problems

After I complained about my Home LTE just dropping Vocacom gave me another test router that worked perfectly. So I send me router in to be replaced with the other model router that worked perfect. Now they send me back the same model router as the first and not even 5 hours the internet is dropping again. The job number is ***8. Please just give me the same model as the test router and all the problems will be solved. We tested it with the technician and he agreed the other router model works well. Please can we sort out this long ongoing problem.