If you are in DR get a flota or a calling plan from Claro that allow free call between the number. Use one of the SIM card with a cell gateway. Use the a sip lie to to call the number to UK(since you have a UK DID). After dialing the UK number transfer the call to your mobile number (Claro to Claro free of charge and crystal clear call). If the call come from UK them it is transferee to your mobile number without charge.