Talk to General Practitioner on Vaccination

My father got vaccinated with Pfizer in ksa but now he is in Karachi, he tried to get vaccinated with second dose also with Pfizer but hospitals are not providing him bcz he came on exit instead they suggested to get vaccinated with moderna vaccine (they says it has the same formula as Pfizer), my question is, is it ok to get combination of vaccines like first dose of Pfizer and now moderna two doses. Kindly guide me