Sms service blocked by pta due to too many messages ,counting as spam

i am a member of my local community and i send sms of different events like death,milads,majalis etc to more than 200 persons to my community. PTA once blocked my sms service as they find it spam and said if more than 200 sms are sent within 15 minutes then sms service is blocked.

i managed to unblock my sms service by sending them applications.
now i send the sms in groups to the receivers in the interval of 15 minutes so that my sms service doesn’t get blocked by PTA again. however this is very inconvenient .

Is there any way that i could send more than 200 sms in 15 minutes i.e i could send sms to all my community (250 numbers appx) at once ?
do i have to register somewhere? is there any procedure?

Sending bulk sms via personal SIM is not a good ideas. You need to get commercial services for that purpose.

Use different SIMs at the same time.