Poor service and unnecessary callout fees

Im very dissapointed with the way they conduct their business. Ive been with this company for 5years and We never had issues until recently. I called them in January because i lost signal, and they charged me R781 and within 3 days after their technician has came, i lost signal again and i called them again where in we fought over the call out fee,l for the same problem, i lost signal again for the third tim le withonh 30days and this time the technician told me that he found that the problem was their aerial, they replaced it and now they are telling me i need to R2900, my concern is why should i pay such an amount of money for a problem that wasnt well fixed by your technicians. And my second question is why should i pay R2900 where as the new application is R2500? This doesnt make sense