Betacard is the brand name of a medicine called atenolol. Amlopres-AT is a fixed dose combination of two medicines: atenolol either 25 mg or 50 mg and amlodipine 5 mg. Thus what you are asking is whether you should take two instead of one medicine. You have also not given the dose of atenolol you are taking.
If your blood pressure is controlled by atenolol with a total dose of 100 mg daily, then naturally there is no need add one more medicine. On the other hand if your blood pressure is no longer controlled with atenolol 100 mg, then definitely there is a need to add another drug.
Looking at your particulars, I should think that the additional medicine should be a diuretic-cum-antihypertensive agent such as slow-release indapamide (Indicontin Continus 1.5 mg once daily in the morning). There is now international consensus that diuretic should be either the first, or at least second drug in anti-hypertensive therapy.
Needless to say non-drug measures must also be taken: brisk walk for 45 minutes daily to cover no less than 4.5 km and reduction of weight to normal value. For a person with a height of 155 cm, you need to bring down your weight by at least 6 kg.