You have three years of experience in your job, which is very good and this experience will help you make more progress in your career in the future. Some of their policies or their turnover is not such that they can give more promotion or increment to their employees and if your company is also one of them then you should consider switching to another company.
If we talk about MBA, it will prove to be a very good option that will get you job offers in even bigger multinational companies. By the way, it would be better if you choose the subject according to your interest, but still, if you want to advance your career in sales, then you choose the option of marketing, your job experience will also be useful in this.
MBA is a job-oriented course and you can do it either in regular or correspondence mode. If you want to do an MBA along with a job then you should choose Correspondence. Marketing is a very nice but also a competitive field. During this course, the nuances of marketing are taught. To make a career in this field, your communication should be attractive.
Choosing the right MBA course through distance education can be tough, so keep these things in mind. Check the affiliation of the institute and see if it is recognized by Distance Education Council and University Grants Commission. Some of the top colleges for MBA are -
Institute of Management Technology Ghaziabad,
Symbiosis Center for Distance Learning,
Indira Gandhi National Open University,
Sikkim Manipal University,