CELLPHONES CONTRACT

I was contacted by one of their consultants for cellphone contract which was during February, n that person told me about Samsung A35 n I will pay R400 a month. But for my surprise they delivered another device of which I didn't ordered for, n I called they client service to come n collect it back as it was wrong . They keep on promising to send delivery vehicle to come but in the meantime they were deducting my money three months without their phone or simcard . They only send courier during June month to collect it n promise to bring back the right device but still there is no phone but they keep on calling me for their payment so I really don't know what to do with these people.